uncorrected proof uncorrected proof

Genet Resour Crop Evol DOI 10.1007/s10722-008-9372-4

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Wheat genetic resources enhancement by the International Maize and Wheat Improvement Center (CIMMYT) Rodomiro Ortiz Hans-Joachim Braun Jose´ Crossa Jonathan H. Crouch Guy Davenport John Dixon Susanne Dreisigacker Etienne Duveiller Zhonghu He Julio Huerta Arun K. Joshi Masahiro Kishii Petr Kosina Yann Manes Monica Mezzalama Alexei Morgounov Jiro Murakami Julie Nicol Guillermo Ortiz Ferrara J. Ivań Ortiz-Monasterio Thomas S. Payne R. Javier Penã Matthew P. Reynolds Kenneth D. Sayre Ram C. Sharma Ravi P. Singh Jiankang Wang Marilyn Warburton Huixia Wu Masa Iwanaga

15 16 17 18 19 20 21 22 23 24 25 26 27

Abstract The International Maize and Wheat Improvement Center (CIMMYT) acts as a catalyst and leader in a global maize and wheat innovation network that serves the poor in the developing world. Drawing on strong science and effective partnerships, CIMMYT researchers create, share, and use knowledge and technology to increase food security, improve the productivity and profitability of farming systems and sustain natural resources. This peoplecentered mission does not ignore the fact that CIMMYT’s unique niche is as a genetic resources enhancement center for the developing world, as shown by this review article focusing on wheat.

A1 A2 A3 A4 A5 A6 A7 A8 A9 A10 A11 A12 A13

R. Ortiz (&) H.-J. Braun J. Crossa J. H. Crouch G. Davenport J. Dixon S. Dreisigacker E. Duveiller Z. He J. Huerta M. Kishii P. Kosina Y. Manes M. Mezzalama A. Morgounov J. Murakami J. Nicol G. Ortiz Ferrara J. I. Ortiz-Monasterio T. S. Payne R. J. Penã M. P. Reynolds K. D. Sayre R. C. Sharma R. P. Singh J. Wang M. Warburton H. Wu M. Iwanaga Centro Internacional de Mejoramiento de Maı´z y Trigo (CIMMYT), Km. 45 Carretera Me´xico-Veracruz, Col. El Batań, Texcoco, Edo. de Mexico 56130, Mexico e-mail: [email protected]

A14 A15 A16 A17

A. K. Joshi Department of Genetics and Plant Breeding, Institute of Agricultural Sciences, Banaras Hindu University, Varanasi, UP, India

Received: 7 April 2008 / Accepted: 25 August 2008 Springer Science+Business Media B.V. 2008

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RESEARCH ARTICLE

CIMMYT’s value proposition resides therefore in its use of crop genetic diversity: conserving it, studying it, adding value to it, and sharing it in enhanced form with clients worldwide. The main undertakings include: long-term safe conservation of world heritage of both crop resources for future generations, in line with formal agreements under the 2004 International Treaty on Plant Genetic Resources for Food and Agriculture, understanding the rich genetic diversity of two of the most important staples worldwide, exploiting the untapped value of crop genetic resources through discovery of specific, strategically-important traits required for current and future generations of target beneficiaries, and development of strategic germplasm through innovative genetic enhancement. Finally, the Center needs to ensure that its main products reach end-users and improve their livelihoods. In this regard, CIMMYT is the main international, public source of wheat seedembedded technology to reduce vulnerability and alleviate poverty, helping farmers move from subsistence to income-generating production systems. Beyond a focus on higher grain yields and valueadded germplasm, CIMMYT plays an ‘‘integrative’’ role in crop and natural resource management research, promoting the efficient use of water and other inputs, lower production costs, better management of biotic stresses, and enhanced system diversity and resilience.

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Genet Resour Crop Evol

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Keywords Triticum Biofortification Climate change Food safety Genetic broadening Modeling Participatory varietal selection Plant breeding Rusts Scab

61 62 63 64

Abbreviations AA ARI BNI CAZS-NR

65

CGIAR

66

CIMMYT

67 68

CTD CWANA

69 70

DON FAO

71

FAWWON

72 73

FHB FONTAGRO

74 75 76

GBSSI GE ICAR

77

ICARDA

78

ITPGRFA

79

IWIN

80 81

MEs IWWIP

82 83 84 85

LD MAS MODPED NARS

86 87 88 89 90

NIRS NIV OSS OSU PCR

PVS QTL RWC

SELBLK SHL SMTA RCT ZEN

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Association analysis Advanced research institutes Biological nitrification inhibition Center for Arid Zone Studies-Natural Resources Consultative Group on International Agricultural Research Centro Internacional de Mejoramiento de Maı´z y Trigo Canopy temperature depression Central and West Asia and Northern Africa Deoxynivalenol Food and Agriculture Organization of the United Nations Facultative and Winter Wheat Observation Nursery Fusarium head blight Fondo Regional de Tecnologıá Agropecuaria Granule-bound starch synthase Genotype-by-environment Indian Council of Agricultural Research International Center for Agricultural Research in the Dry Areas International Treaty on Plant Genetic Resources for Food and Agriculture International Wheat Improvement Network Mega-environments International Winter Wheat Improvement Program Linkage disequilibrium Marker-assisted selection Modified pedigree/bulk method National Agricultural Research Systems Near-infrared spectroscopy Nivalenol Office of Special Studies Oregon State University Polymerase chain reaction

91 92 93 94

95 96 97 98 99 100

Wheat general overview

101

For millennia wheat has provided daily sustenance for a large proportion of the world’s population. It is produced in a wide range of climatic environments and geographic regions (Table 1). During 2004–2006, the global annual harvested area of ‘‘bread wheat’’ and ‘‘durum wheat’’ averaged 217 million ha, producing 621 million t of grain with a value of approximately US$ 150 billion. About 116 million ha of wheat was grown in developing countries, producing 308 million t of grain (FAO 2007) with a value of approximately US$ 75 billion. Wheat serves a wide range of demands for different end-uses, including staple food for a large proportion of the world’s poor farmers and consumers. The similarity between average yields in developed and developing regions is deceptive: in developed countries around 90% of the wheat area is rainfed while in developing countries more than half of the wheat area is irrigated, especially in the large producers (India and China). In addition, there are large differences in productivity between countries within the two groups of countries, and even between countries deploying similar agronomic practices. For instance, among major rainfed producers (over 1 million ha) the average national yield ranges from about 0.9 t ha-1 in Kazakhstan to 2.6 t ha-1 in Canada, and up to 7.9 t ha-1 in the United Kingdom (FAO 2007). Similarly, contrasts are seen amongst irrigated producers, e.g. India has an average yield of 2.6 t ha-1 vis-a`-vis 6.5 t ha-1 in Egypt. Thus, there is clearly considerable scope for increasing productivity in many countries.

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SAGARPA

Participatory variety selection Quantitative trait loci Rice-Wheat Consortium for the Indo-Gangetic Plains Secretarıá de Agricultura Ganaderıá. Desarrollo Rural Pesca y Alimentacioń (Mexico) Selected bulk method Seed Health Laboratory Standard Material Transfer Agreement Resource conserving technology Zearalenone



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Genet Resour Crop Evol Table 1 Area and productivity of wheat in selected regions (2004– 2006)

Region

Area (million ha) 26

5.3

137

East Asia

23

4.3

98

South Asia (including 2.2 million ha in Afghanistan) North America

38 31

2.5 2.8

97 88 22

9

2.4

Middle East and North Africa (including Turkey)

27

2.3

61

Eastern Europe and Russia

31

2.2

69

15

1.4

22

13

1.5

19

4

2.3

9

217

2.9

621

116

2.7

308

101

3.1

313

12

0.9

12

10

2.6

27

2

7.9

15

26

2.6

70

1

6.5

8

Central Asia and Caucasus Australia and New Zealand

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Production (million t)

European Union 27

South America

Other (including 3 million ha in sub-Saharan Africa) World Developing countries Developed countries (incl. former-USSR) Country contrasts …dominated by rainfed production Kazakhstan

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Canada

United Kingdom

…dominated by irrigated production India Egypt

Source: FAO (2007)

The relative importance of wheat as a staple in selected countries is displayed in Fig. 1. Wheat provides 500 kcal of food energy capita-1 day-1 in the two most populous countries in the world, China and India, and over 1,400 kcal capita-1 day-1 in Iran and Turkey. Overall across in the developing world, Fig. 1 Wheat share in food consumption in selected countries (Source data: FAO 2007)

16% of total dietary calories come from wheat (cf. 26% in developed countries) second only to rice in importance. As the most traded food crop internationally, wheat is the single largest food import into developing countries and, also, a major portion of emergency food aid.

4500

All foods Wheat

4000 3500

minimum daily requirement

3000 2500 2000 1500 1000

500

R

U S us A si Fr an an C ce an G ada er m a Tu ny rk Pa ey ki s Au tan st ra l U ia kr ai ne U K Ar Ira ge n Ka nt za ina kh st a Po n la nd Eg yp t R Italy om a U zb nia ek is ta n

na hi

In

di a

0

C

Kcal/capita/day

133 134 135 136 137 138

Yield (t ha-1)



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Wheat made a significant contribution to the increase in global food production during the past four decades as total production rose steadily through the use of higher-yielding, water and fertilizerresponsive and disease-resistant cultivars supported by strengthened input delivery systems, tailored management practices, and improved marketing (Braun et al. 1998; Dixon et al. 2006) The increased grain production attributable to improved germplasm alone has been valued at up to US$ 6 billion year-1 (Lantican et al. 2005). The increased production of wheat (and other staples) led to lower food prices (von Braun 2007), which contributed to a reduction in the proportion of poor in developing countries (Chen and Ravallion 2007). Looking to the future, the global population is projected to steadily increase, albeit at a decreasing rate compared to the past century, to around nine billion in 2050. The food and other needs of the growing population underpin the strong demand for cereals. The demand for wheat, based on production and stock changes, is expected to increase from 621 million t during 2004–2006 to 760 million tons in 2020 (Rosegrant et al. 2001), to around 813 million t in 2030, and to more than 900 million t in 2050 (FAO 2006, 2007; Rosegrant et al. 2007) implying growth rates of 1.6% for 2005– 2020, 1.2% for 2005–2030, and 0.9% for 2005–2050.

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The International Wheat Improvement Network

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The history of the International Maize and Wheat Improvement Center (CIMMYT) involvement in wheat improvement begins in the 1940s, more than 20 years before it was officially founded as an international organization in 1966 (Ortiz et al. 2007b). Its roots reach back to the Office of Special Studies (OSS), a research project sponsored by the Mexican government and the Rockefeller Foundation that was dedicated to improving maize, beans and wheat, and later potatoes. The OSS began as a research and training program focused on Mexico, but soon began collaborating with other countries, especially in South America. The OSS developed the key organizational principles that would eventually become central to the entire network of the Consultative Group on International Agricultural Research (CGIAR) centers. The OSS wheat program, led by Nobel Peace Laureate Norman E. Borlaug, did crop

breeding along with on-farm research and extension demonstrations aimed at introducing new technology to producers. For many decades the global average yield of wheat has increased, supported by an effective International Wheat Improvement Network (IWIN), an alliance of National Agricultural Research Systems (NARS), CIMMYT, the International Center for Agricultural Research in the Dry Areas (ICARDA) and advanced research institutes (ARI). This alliance has deployed cutting-edge science alongside practical multi-disciplinary applications resulting in the development of germplasm, which has improved food security and the livelihoods of farmers in developing countries. For example, during the late 1950s and 1960s, researchers in Mexico, under the leadership of Borlaug, developed the improved spring wheat germplasm, which launched the Green Revolution in India, Pakistan, and Turkey (Reynolds and Borlaug 2006). Collaboration was broadened during the 1970s to include Brazil, China, and other major developing country producers, and resulted in wheat cultivars with broader disease resistance, better adaptation to marginal environments, and tolerance to acid soils. During the 1980s, an international collaborative partnership between Turkey, CIMMYT, and ICARDA was established for winter wheat improvement in developing countries. The IWIN currently operates field evaluation trials in more than 250 locations in around 100 countries for testing improved lines of wheat in different environments. As a publicly-funded international research institute, CIMMYT regards its research products as international public goods. The main objective for regional and global multi-location testing is the identification of useful genetic diversity that will lead to research products, parental germplasm, or ultimately cultivars adapted to targeted wheat-production environments and systems in the developing world. Multi-location testing and data exchange increase the selection efficiency of participating wheat breeders. Returned data are used to identify parents for subsequent crosses and to incorporate new genetic variability into advanced lines that are consequently able to cope with the dynamics of abiotic and biotic stresses affecting wheat farming systems. With the growing research capacity of NARS in many major wheat-producing countries, the number of wheat cultivars released annually by developing

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countries doubled to more than 100 cultivars by the early 1990s (Lantican et al. 2005). The early era of improved cultivars spread rapidly over the high potential production areas in most developing regions. Widespread adoption occurred most rapidly in South Asia, especially in irrigated areas, followed by the rainfed areas of Latin America; adoption has been slower in the Middle East, North Africa, and sub-Saharan Africa because of drier riskier environments and weaker institutions (Evenson and Gollin 2003; Lantican et al. 2005). With such widespread adoption accompanied by yield increases, average annual rates of return for investments in wheat research averaged around 50% year-1 (Alston et al. 2000). In addition, the urban poor benefited substantially as production increases drove down wheat prices.

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The wheat genetic resources endowment

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By the 1920s it was acknowledged that wheat cultigens of the genus Triticum L. belonged to three ploidy groups with chromosomes number of 2n = 2x = 14 (T. monococcum L.), 28 (T. turgidum L. and T. timopheevii Zhuk.), and 42 (T. aestivum L. em. Thell. and T. zhukovskyi Menabde & Ericz.). However, world wheat production is almost entirely based on two species: T. aestivum—also known as common or bread wheat, which account for about 95% of world production, and T. turgidum ssp. durum (Desf.) Husn.—known as macaroni or durum wheat, which accounts for the remaining 5%. The other cultivated species are largely historical relics. Genetic resources in wheat can be categorized into six broad groups (Frankel 1977; FAO 1983), namely modern cultivars in current use, obsolete cultivars— often the elite cultivars of the past and often found in the pedigrees of modern cultivars, landraces, wild relatives of crop species in the Triticeae Dumort. tribe, genetic and cytogenetic stocks, and breeding lines. These genetic resources represent the gene pool potentially available to breeders and other users of collections. This broad pool can be further subdivided into primary, secondary, and tertiary gene pools (Harlan and de Wet 1971). The primary pool consists of the biological species, including cultivated, wild, and weedy forms of the crop, and gene transfer in this group is considered to be easy. The secondary gene

pool has the coenospecies (or a group of ‘‘allies’’ or ‘‘relatives’’ to a given taxon) from which gene transfer is possible but difficult, while the tertiary gene pool is composed of species from which gene transfer is possible but only with great difficulty. Clearly, the boundaries of these groups are fuzzy and also change with changes in technology. Consequently, several authors including Smartt (1984) and Konarev et al. (1986) have suggested the gene pools concept of Harlan and De Wet (1971) be modified to increase the number of gene pools from three to four to coincide with populations, species, genera, and tribes, respectively (Merezhko 1998). Unfortunately, even this simple concept is difficult to apply in wheat because of the lack of an accepted view on the classification of wheat species, the genus Triticum, and even the tribe Triticeae (von Bothmer et al. 1992; Merezhko 1998). The Wheat Genetics Resource Center at Kansas State University in the USA provides a comprehensive online source of information about wheat taxonomy, including a detailed comparison of the most often used classifications, as part of the GrainTax project (www.k-state.edu/wgrc/). Herein we will follow the most recent taxonomic treatment of Triticum and Aegilops L. of van Slageren (1994), which updated previous research by Hammer (1980) on the taxonomy and nomenclature of the genus Aegilops. The cultivated species of Triticum and their genomic constitution are given in Table 2. It should be noted that there are two valid biological species at each ploidy level. The diploid T. monococcum L. has both cultivated and wild forms, while T. urartu Tumanian only exists in the wild. Both tetraploid forms exist in both cultivation and in the wild, while both hexaploid species only exist in cultivation. The distribution of these species is described by Gill and Friebe (2002). Aegilops is the most closely related genus to Triticum and has been widely used in wheat improvement. All Aegilops are annuals. The genus consists of 11 diploid species and 12 polyploid species, including tetraploids and hexaploids (Table 3). Their taxonomy and distribution is discussed by van Slageren (1994). Dasypyrum [Haynaldia] villosum (L.) Cand. is among the Triticeae species and is also a genetic resource for wheat breeding. It is an annual with a V genome and is easily hybridized to durum or bread wheat. Each of the chromosomes was added to common wheat by the late E. Sears (Global Crop Diversity Trust 2007).

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Genet Resour Crop Evol Table 2 Species of genus Triticum and their genomic constitution (After Gill and Friebe 2002)

Species

Genomic constitution

Triticum aestivum L.

Nuclear

Organellar

ABD

B (rel. to S)a

Triticum aestivum ssp. aestivum (common or bread wheat) Triticum aestivum ssp. compactum (Host) Mackey (club wheat) Triticum aestivum ssp. macha (Dekapr. & A. M. Menabde) Mackey

PR OO F

Triticum aestivum ssp. Spelta (L.) Thell. (large spelt or dinkel wheat)

Author Proof

Triticum aestivum ssp. sphaerococcum (Percival) Mackey (Indian dwarf wheat) Triticum turgidum L.

AB B (rel. to S) Triticum turgidum ssp. carthlicum (Nevski) A. Lo¨ve & D. Lo¨ve (Persian wheat) Triticum turgidum ssp. dicoccoides (Ko¨rn. ex Asch. et Graebn.) Thell. (wild emmer) Triticum turgidum ssp. dicoccon (Schrank) Thell. (emmer wheat)

Triticum turgidum ssp. durum (Desf.) Husn. (macaroni or durum wheat)

Triticum turgidum ssp. paleocolchicum (Dekapr. et Menabde) Mac Key ex Hanelt Triticum turgidum ssp. polonicum (L.) Thell. (Polish wheat) Triticum turgidum ssp. turanicum (Jakubz.) A. Lo¨ve & D. Lo¨ve (Khorassan wheat) Triticum turgidum ssp. turgidum (pollard wheat)

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Triticum zhukovskyi Menabde & Ericz. Triticum timopheevii (Zhuk.) Zhuk.

AtAmG

A (rel. to S)

AtG

G (rel. to S)

Triticum timopheevii ssp. Armeniacum (Jakubz.) Slageren (wild form)

Triticum timopheevii ssp. timopheevii (cultivated form) Triticum monococcum L.

Am

Am

Triticum monococcum ssp. aegilopoides (Link) Thell. (wild form) Triticum monococcum ssp. monococcum (einkorn or small spelt wheat)

a

Related to S-genome species, cf. Table 3

335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354

Triticum urartu Tumanian ex Gandilyan (wild form)

In addition to Aegilops, a host of more distantly related annual and perennial members of related genera in the Triticeae have potential as sources of germplasm in wheat breeding including cultivated rye and barley and their near relatives, as well as a host of perennial grasses. The bulk of the perennial Triticeae species have been difficult to exploit in wheat improvement primarily because their genomes are non-homologous to those of wheat, and genetic transfers cannot be made by homologous recombination. However, gene transfer is possible via complex cytogenetic protocols. Over the last three decades hybridization per se has become less of a problem in inter-specific hybridization between Triticum species and more distantly related genera, although achieving timely practical outcomes using cytogenetic techniques is difficult in genera other than Secale L. and Thinopyrum (Mujeeb-Kazi and Rajaram 2002). Nevertheless, variation for economically-important traits such as host plant resistance to

A

A

the cereal rusts, salt-tolerance, and resistance to barley yellow dwarf virus have been transferred from perennial wild species into bread wheat. The diseaseresistant genes have been used in modern wheat cultivars. Mujeeb-Kazi and Hettel (1995) provided a comprehensive account of interspecific hybridization in the Triticeae. The perennial genera of the tribe Triticeae of interest in wheat improvement are given in Table 4 along with their genome designations and ploidy levels. All the genomes of the perennial Triticeae have been combined with the A, B, and D genomes of bread wheat (Mujeeb-Kazi 1995).

355 356 357 358 359 360 361 362 363 364 365 366

Wheat ex situ conservation strategy

367

Due to the strategic importance of wheat in food security and trade in many countries, and the critical importance of breeding in ensuring national industries remain competitive, over 80 autonomous germplasm

368 369 370 371



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Genet Resour Crop Evol Table 3 Aegilops species and their genomic constitution (After Gill and Friebe 2002 and modified as per chromosome pairing and DNA analysis following Dvorak 1998) Species

Genomic constitution Nuclear Sb

Aegilops bicornis (Forssk.) Jaub. & Spach

Sb o

UM (UM )

U

Aegilops markgrafii (Greuter) K. Hammer (known as Aegilops caudata auct non L.)

C

C

UM (UXco)

U2

M

M

PR OO F

Aegilops biuncialis Vis. Aegilops columnaris Zhuk.

Author Proof

Organellar

Aegilops comosa Sm. in Sibth. & Sm. spp. heldreichii (Holzm. ex Boiss.) Eig Aegilops crassa Boiss.

c1

c

c1 c

c1

c2

c

D M (D X )

var. glumiaristata Eig

c1

c2 c

D D M (D D X )

Aegilops cylindrica Host Aegilops geniculata Roth (syn. Ae. ovata auct. non L.) Aegilops juvenalis (Thell.) Eig Aegilops kotschyi Boiss. Aegilops longissima Schweinf. & Muschl. Aegilops mutica Boiss. var. recta (Zhuk.) Hammer

Aegilops peregrina (Hack. in J. Fraser) Maire & Weiller (syn. Ae. variabilis)

–

DcCc

D

UM (UMo)

Mo

DMU (DcXcUj)

D2

US (US1) S1

Sv S12

T

T,T2

n

UN CO RR EC TE D

Aegilops neglecta Req. ex Bertol. (syn. Ae. triaristata)

D2

UM (UX )

U

UMN (UXtN)

U

US (US1)

Sv

S

s

Sv

Aegilops sharonensis Eig

S

sh

S1

Aegilops speltoides Tausch

S

S,G,G2

Aegilops tauschii Coss. var. tauschii, var. strangulata (Eig) Tzvel.

D

D

Aegilops triuncialis L.

UCt

U,C2

Aegilops searsii Feldman & Kislev ex Hammer

Aegilops umbellulata Zhuk.

U

U

Aegilops uniaristata Vis.

N

N

Aegilops vavilovii (Zhuk.) Chennav.

DMS (DcXcSv)

Aegilops ventricosa Tausch

v

v

DN

D2 D

Underlined genomes are modified at the polyploidy level; those in brackets were deduced from DNA analysis

372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387

collections holding an estimated excess of 800,000 accessions have been established globally. These collections vary in size and coverage; the largest have over 100,000 accessions and the smallest a few hundred. They also vary greatly in coverage. Most collections evolved from breeders’ working collections and carry predominantly local or regional cultivars—advanced, obsolete or landrace—as well as introduced cultivars of interest to national or regional breeders. There is often substantial duplication within, and certainly between these sorts of collections. Virtually every wheat collection in the world would carry common popular cultivars such as ‘Marquis’ and ‘Bezostaya 1.’ However, there are also numerous small specialist collections of wild wheat relatives and genetic stocks.

An important issue in developing a global strategy for the conservation of wheat genetic resources is deciding on the diversity of accessions to be included in the strategy (Merezhko 1998). One extreme view would be to limit the network to the primary gene pool—the cultivated species and the closely-related species with which they can be readily hybridized. The other extreme is that in the modern world of transgenics all biological species are potential genetic resources for wheat breeding and the concepts of primary, secondary, and tertiary gene pools are quaint and outmoded. It is suggested here, following Merezhko (1998), that we should restrict our focus to Triticum species and related genera of the Triticeae. This coverage aligns with the intention of the International Treaty on Plant Genetic Resources for Food and Agriculture (ITPGRFA).



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Genome

Species

Genome

Agropyron cristatum (L.) Gaertn.

PP

Leymus angustus (Trin.) Pilger

NNNNNNXXXXXX

Agropyron cristatum

PPPPPP

Leymus arenarius (L.) Hochst.

NNNNXXXX

Agropyron desertorum (Fisch. ex Link) Schult.

PPPP

Leymus chinensis (Trin.) Tzvelev

NNXX

Agropyron fragile (Roth) P. Candargy

PP

Leymus cinereus (Scribn. & Merr.) A. Lo¨ve

NNXX

Agropyron michnoi Roshev.

PPPP

Leymus innovatus (Beal) Pilger

NNXX

Agropyron mongolicum Keng

PP

Leymus mollis (Trin.) Pilger

NNXX

´ . Lo¨ve WW Australopyrum pectinatum (Labill.) A

Leymus racemosus (Lam.) Tzvelev

NNNNXXXX

Elymus abolinii (Drobow) Tzvelev ´ . Lo¨ve Elymus alatavicus (Drobow) A

SSYY

Leymus salinus (M.E. Jones) A. Lo¨ve

NNXX

SSYYPP

Leymus triticoides (Buckl.) Pilger

NNXX

Elymus arizonicus (Scribn. & J. G. Sm.) Gould ´ . Lo¨ve Elymus batalinii (Krasn.) A

SSHH

Pascopyrum smithii (Rydb.) A. Lo¨ve

SSHHNNXX

SSYYPP

Psathyrostachys alatavicus

NN

Elymus canadensis L.

SSHH

Psathyrostachys fragilis (Boiss.) Nevski

NN

Elymus caninus (L.) L.

SSHH

Psathyrostachys huachanica Keng

NN

Elymus ciliaris (Trin.) Tzvelev

SSYY

Psathyrostachys junceus (Fisch.) Nevski

NN

PR OO F

Species

Elymus dahuricus Turcz. ex Griseb.

SSHHYY

Psathyrostachys kronenburgii (Hackel) Nevski

NN

Elymus drobovii Turcz. ex Griseb.

SSHHYY

SSPP

Elymus gmelinii (Ledeb.) Tzvelev ´ . Lo¨ve Elymus grandiglumis (Keng) A

SSYY

Pseudoroegneria deweyii Jensen, Hatch & Wipff ´ . Lo¨ve Pseudoroegneria tauri (Boiss. & Balansa) A

SSYYPP

Pseudoroegneria libanotica (Hackel) D. R. Dewey

SS, SSSS

Elymus kamoji (Ohwi) S. L. Chen ´ . Lo¨ve Elymus kengii (Tzvelev) A

SSHHYY

Pseudoroegneria spicata (Pursh) A. Lo¨ve

Elymus longearistatus (Boiss.) Tzvelev

SSYY

Elymus panormitanus (Parl.) Tzvelev ´ . Lo¨ve Elymus parviglume(Keng) A

SSYY

Elymus pendulinus (Nevski) Tzvelev

SSYY

Thinopyrum caespitosum C. Koch) Barkw. et D. R. Dewey

EESS

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Table 4 The nuclear genome of the perennial species of the tribe Triticeae (after Mujeeb-Kazi and Wang 1995)

SSYYPP SSYY

SSPP

SS, SSSS ´ . Lo¨ve SS, SSSS Pseudoroegneria stipifolia (Czern. ex Nevski) A ´ . Lo¨ve Pseudoroegneria strigosa (M.Bieb.) A SS, SSSS Secale montanum = Secale strictum (Presl) Presl. RR ´ . Lo¨ve JJ Thinopyrum bessarabicum (Sa˘vul. & Rayss) A

Elymus shandongensis B. Salomon

SSYY

SSHH

Thinopyrum curvifolium (Lange) D. R. Dewey ´ . Lo¨ve Thinopyrum distichum (Thunb.) A

JJJJ

Elymus sibiricus L.

´ . Lo¨ve Elymus strictus (Keng) A

SSYY

Thinopyrum elongatum (Host) D. R. Dewey

EE

Elymus tsukushiensis Honda

SSHHYY

Thinopyrum intermedium (Host) Barkworth & D. R. Dewey

JJJJSS, JJEESS, EEEESS

Elymus ugamicus Drobow

SSYY

JJEE

Thinopyrum junceiforme (A. & D. Lo¨ve) A. Lo¨ve

JJEE

Elymus vaillantianus (Wulfen ex Schreb.) K. SSHH B. Jensen

Thinopyrum junceum (L.) A. Lo¨ve p.p.

JJJJEE

Elytrigia repens (L.) Desv. ex B. D. Jackson SSSSHH

Thinopyrum nodosum [= Lophopyrum nodosum ´ . Lo¨ve] (Nevski) A

EESS

Hordeum bogdanii Wilensky

HH to HHHHHH

JJJJEEEEEE

Hordeum brevisubulatum Link

HH to HHHHHH

Thinopyrum ponticum (Podp.) Z.-W. Liu & R.-C. Wang ´ . Lo¨ve Thinopyrum sartorii (Boiss. & Heldr.) A

Hordeum iranicum (Bothmer) Tzvelev

HH to HHHHHH

Thinopyrum scirpeum (C.Presl) D. R. Dewey

EEEE

Hordeum jubatum L.

HH to HHHHHH

Thinopyrum scythicum

EESS

Hordeum violaceum Boiss. & Hohen.

HH to HHHHHH

Thinopyrum turcicum

JJJJEEEE



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The growing size and sophistication of genetic and molecular stock collections is testimony to their increasing contributions to enable the effective utilization of the variation conserved in ‘‘traditional’’ germplasm collections. The role of genetic stock collections in the global conservation effort of wheat germplasm should be re-evaluated and these should be given a higher priority in a rationalized system than they had in the past. The Global Wheat, Rye, and Triticale Conservation Strategy (Global Crop Diversity Trust 2007) suggested that the following criteria are essential for an efficient and effective global system for the conservation of wheat genetic resources: globally or regionally-important, accessible under the internationally agreed terms of access and benefit sharing provided for in the multilateral system as set out in the ITPGRFA, committed to the long-term conservation of the unique

resources it holds, well-managed and in conformity with agreed upon scientific and technical standards of management, maintaining effective links to users of plant genetic resources, and an indicated willingness to act in partnership with others to achieve a rational system for conserving wheat genetic resources. Twenty-three private, national, and global collections that fulfilled these criteria where identified as key partners for a global wheat conservation network (Table 5). The proposed wheat conservation strategy focuses on the conservation and use of the full spectrum of the genetic resources of wheat with the exception of the perennial wild relatives. Modern and obsolete improved cultivars are generally well-conserved in global wheat germplasm collections because many such collections either were derived from breeders working collections or were primarily established to

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Table 5 Collections of a global network of wheat genetic resources Country Global USA Russia Global India Australia France Iran Czech Republic Ethiopia Bulgaria Germany

Institute

No. of accessions

CIMMYT, El Batan, Mexico

111,681

USDA-ARS, National Small Grains Facility, Aberdeen, Idaho

56,218

N.I. Vavilov Research Institute of Plant Industry (VIR), St. Petersburg

39,880

ICARDA, Aleppo, Syria

37,830

National Bureau of Plant Genetic Resources (NBPGR), New Delhi

32,880

Australian Winter Cereals Collection, Tamworth

23,917

INRA Station d’Amelioration des Plantes, Clermont-Ferrand

15,850

National Genebank of Iran, Genetic Resources Division, Karaj

12,169

Research Institute of Crop Production, Prague

11,018

Plant Genetic Resources Centre, Institute of Biodiversity Conservation and Research, Addis Ababa

10,745

Institute for Plant Genetic Resources ‘‘K. Malkov’’, Sadovo

9,747

Genebank, Institute for Plant Genetics and Crop Plant Research (IPK), Gatersleben

9,633

United Kingdom Department of Applied Genetics, John Innes Centre, Norwich

9,584

Cyprus

National Genebank (CYPARI), Agricultural Research Institute, Nicosia

7,696

Genetic Resources Management Section, NIAR (MAFF), Tsukuba Station Federale de Recherches en Production Vegetale de Changins, Nyon

7,148 6,996

Japan Switzerland Turkey Netherlands Canada USA

Plant Genetic Resources Department, Aegean Agricultural Research Institute, Izmir

6,381

Centre for Genetic Resources, Wageningen

5,529

Plant Gene Resources of Canada, Winnipeg

5,052

Wheat Genetics Resource Center, Kansas State University, Manhattan

5,000

Japan

Plant Germplasm Institute, Graduate School of Agriculture, Kyoto University

4,378

Spain

Centro de Recursos Fitogeneticos, INIA, Madrid

3,183

Sweden

Nordic Gene Bank, Alnarp

Total

23 institutes

1,843 434,358

Source: Global Crop Diversity Trust (2007)



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service local or regional breeding programs, and these were the accessions most sought by breeders. In fact, many important cultivars are conserved in the majority of national and international collections. The major focus of a global strategy for this category of genetic resource should be to reduce redundancy in the global set of collections to free up resources for other priorities. Landraces have received priority for collection, conservation, and documentation in recent years, supported by the efforts of FAO, the CGIAR, and others because of the increasing threat to their continued existence by the spread of improved modern cultivars. Nevertheless, such cultivars are poorly represented in world collections compared to modern and obsolete cultivars and should remain a priority for the global strategy, both to ensure the collection of material that is not in collections but that still exists in the field and that the long-term conservation of collected material is in line with agreed upon international standards. The wild relatives of wheat are also generally poorly represented in global wheat germplasm collections. There are several reasons for this. First, wild relatives are seldom used in conventional breeding programs as compared to cultivars of the same species and usually require an extensive period of germplasm enhancement. Wild species tend to be collected and used by the small number of specialist institutes concerned with interspecific hybridization. Second, they are more difficult to seed increase and maintain because of their tendency to shatter their seed as compared crop cultivars. For this reason also, the distribution and use of some wild species is limited because of their potential as weeds. Finally, wild species, because of their capacity to selfreproduce in nature, have been seen as under less threat of extinction than the cultivated landraces (Global Crop Diversity Trust 2007). Unfortunately, many populations of the annual wild relatives of wheat, particularly those at the extremes of their distribution that are of special interest for breeding purposes, are under threat because of changing patterns of land use and global warming. At the same time, new technologies have made the use of the annual wild relatives as a germplasm source easier, which has generated an interest and need for representative collections of annual wild relatives to be maintained in accessible

collections. For these reasons the annual wild relatives should clearly be afforded a greater priority in the global wheat germplasm collections than they have had in the past. This is not to suggest that all or many collections need to move to collect or conserve the wild relatives of wheat, but rather, that those with the specialized knowledge and capacity to undertake the collection and conservation of this category of germplasm should be given priority support. As noted above, it can also be argued that defined genetic stock collections should receive greater priority in a balanced global effort to conserve and make available for use the genetic resources of wheat. Again, because specialists need to develop and reliably maintain genetic stocks as true-to-type accessions, it is expected that defined genetic stocks will be maintained by specialized institutes. The emphasis will be to support those institutes to develop a coordinated system that replaces the largely ad hoc system that has operated to date for the conservation of genetic stocks so that valuable material once developed and in the public domain is available on a continuing basis for all who need it. The perennial wild relatives of wheat were not seen as a priority for conservation in the collective global wheat germplasm system. Again, there are several reasons for this. The first, and perhaps most important, is that collections of many of these species are maintained in perennial grass collections for use in breeding programs as grazing species or for other uses. Second, despite the number of perennial wild relatives of wheat that exist, their extensive global spread, and the extensive research that has taken place, the number of examples of commerciallysuccessful gene transfer from perennial wild relatives to wheat remains modest. Third, the perennial wild relatives, like their annual counterparts, require specialized seed increase knowledge and facilities, which is only likely to be available in specialized collections.

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A brief account of wheat breeding at CIMMYT and its impact in grain yield

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The global impact of the wheat breeding program of CIMMYT has been significant and well-documented (Rajaram 1999; Trethowan et al. 2001). Many factors have contributed to CIMMYT’s success, such as breeding targeted to mega-environments (MEs), use

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of a diverse gene pool for crossing, and shuttle breeding (Rajaram et al. 1994; Rajaram 1999; Ortiz et al. 2007a). Another key factor, however, has been the breeding strategies adopted by CIMMYT breeders. In this regard, the monitoring of crop trends provides a means for assessing the success of a breeding program. As can be observed in Fig. 2, wheat yields worldwide increased in a linear manner but in recent years the rate of yield increase has slightly declined. Prior to the Green Revolution, the global average wheat yield was increasing at about 1.5% per annum: around 2.2% per annum in developed countries but growing at less than 1% per annum in developing countries. The Green Revolution boosted the growth of average wheat yields to 3.6% per annum in developing countries during 1966–1979. However, yield growth in developing countries slipped to 2.8% per annum during 1980–1994, and then dropped to 1.1% per annum during 1995–2005, once again falling below the population growth rate. For international wheat breeding, the period from 1951 to date can be divided into well defined improvement eras tracing from the efforts of Borlaug and his colleagues (Ortiz et al. 2007a), which began in the early 1940s, continuing with the efforts of CIMMYT efforts until today and include:

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•

•

•

enhanced levels of stem (Puccinia graminis f. sp. tritici Eriks. & Henn.) and leaf (Puccinia triticina Eriks.) rust resistance and better lodging tolerance 1962–1975—introduction and farmer adoption of semi-dwarf cultivars (it is of interest to note that the initial semi-dwarf cultivars like ‘Pitic 62’ were, in fact, inferior in grain yield, quality and even lodging tolerance to the last developed, nonsemi-dwarfs cultivars like ‘Nainari 60,’ but the clear potential advantage of the semi-dwarf cultivars was readily apparent to both researchers and farmers); and 1975 to date—continued improvement in yield potential, host plant resistance (especially combating the continual breakdown of leaf rust resistance in both bread and durum wheat cultivars, and more recently against the stem rust Ug99 strain) and in the industrial quality of semi-dwarf cultivars.

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The rate of average wheat yield increases in farmer fields in the Yaqui Valley from 1951 to 2005 has been impressive (Table 6). Farmers in this valley were among the first to grow new cultivars ensuing from the work undertaken at the experimental station near Ciudad Obregoń, where Borlaug started breeding the wheat lines of the Green Revolution and this site is still being used by CIMMYT as its main wheat breeding site in Mexico. This trend is representative of similar rates of yield increases that have occurred

1951–1962—introduction and farmer-adoption of improved, non-semi-dwarf cultivars with

Fig. 2 Wheat mean grain yields for the World and in the Yaqui Valley, Sonora, Mexico (1961–2005) (World data source: FAO 2007)

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Yield (kg/ha)

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2

Yaqui Wheat Yield = - 125,222 + 65.45 kg/year; R = 0749 Annual Yield Increase = 1.57%

3500 3000 2500 2000 1500

2

World Wheat Yield = - 80,785 + 41.77 kg/year; R = 0.977 Annual Yield Increase = 2.16%

1000

500 1961

1965

1969

1973

1977

1981

1985

1989

1993

1997

2001

2005

Year FAO World Mean Yld (kg/ha)

Yaqui Valley Farmer Mean Yld (kg/ha)

Linear (FAO World Mean Yld (kg/ha))

Linear (Yaqui Valley Farmer Mean Yld (kg/ha))



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Genet Resour Crop Evol Table 6 Annual rates of increase in average wheat yield in farmer fields in the Yaqui Valley, Sonora, Mexico (1951–2005) Yield increase year-1 (kg ha-1)

Yield increase year-1 (%)

Coefficient of determination (year versus yield)

2.36

81

0.857

Improved non-semi-dwarfs

5.20

110

0.808

First generation semi-dwarf cultivars

3.00

111

0.569

Second generation semi-dwarf cultivars

0.15

9

0.011

-0.43

-23

0.040

44

0.337

Further semi-dwarf cultivar development with modest farmer adoption Second generation semi-dwarf cultivars to date

0.80

593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612

in many other wheat production areas such as India, Pakistan, and China, among many others (especially irrigated production regions), notably since the introduction and adoption of semi-dwarf cultivars with resistance to the various rust diseases (Reynolds and Borlaug 2006). Clearly, the tendency has been towards a reduced rate of yield increases over time. This is a fact of considerable concern and is likely not restricted to the Yaqui Valley as shown by the global trends (Fig. 2). It would appear that factors associated with the declining rate of yield increases in wheat include relatively slow increases in private sector investments during the last decade, and lower applications of production inputs as oil prices drove up the cost of fertilizer and pumping irrigation water while, until very recently, the price of wheat gradually fell. In addition, a lack of attention to crop management and the degradation of resources including soil fertility and quality of water for irrigation, combined with an increasing frequency of droughts.

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Genetic enhancement of spring bread wheat

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The spring bread wheat germplasm developed at CIMMYT is targeted for its adaptation to diverse wheat production environments in the developing world. The breeding program is based in Mexico and shuttles germplasm between two contrasting environments: Ciudad Obregoń (280 N, 32 m.a.s.l.) in northwestern Mexico and Toluca (180 N, 2,640 m.a.s.l.) in the highlands of Central Mexico, thereby achieving two generations a year (Braun et al. 1996). This shuttle breeding exposes wheat materials to diverse photoperiod and temperatures and to a range of important diseases. The lines developed through this process are then tested widely around the world and

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selected materials, based on international performance, are identified for continued crossing. There are two major breeding thrusts at present: germplasm for irrigated areas, and germplasm for rainfed areas.

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Breeding objectives

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Traits of foremost importance in spring wheat improvement include: (1) grain yield potential, stability, and wide adaptation, (2) potential for durable resistance to diseases such as stem, leaf, and yellow (Puccinia striiformis West.) rusts, Septoria tritici blotch, Fusarium head blight or scab, and root rots, (3) water-use efficiency and water productivity, (4) heat tolerance, and (5) end-use quality characteristics. Breeding objectives and schemes are continually modified to maintain the efficiency and effectiveness of germplasm products. For example, as water resources continue to decline, wheat will have to be produced with less water. This requires the development of high-yielding cultivars that are also efficient in water use for irrigated areas or have improved performance under drought for rainfed areas. Expansion of resource-conserving technologies, for example zero-tillage in many countries not only reduces production costs but also increases long-term sustainability. However, it is evident that breeding objectives must be modified to develop a different kind of germplasm that has better emergence and growth characteristics and resistance to those diseases and pests that survive on residues (Joshi et al. 2007a).

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Yield potential, yield stability, and wide adaptation

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The yield potential of semi-dwarf wheat cultivars, irrespective of their origin, has continued to increase at

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Periods of cultivar development



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the rate of about 1% annually. Yield stability and wide adaptation are important traits that must be present together with yield potential to ensure that a genotype maintains its superiority in diverse environments, management practices, and biotic and abiotic stresses. Breeding for specific adaptations has not been very successful because in most areas, temperatures and rainfall patterns shift annually. The wide adaptation and stable performance of CIMMYT-derived wheat lines and cultivars are largely due to shuttle breeding in Mexico where segregating populations are selected in two contrasting environments under diverse diseases and abiotic stresses, followed by international multi-location testing of advanced lines. This approach is capable of identifying the best stable performers in a single year of testing. Various studies have shown that increases in yield potential are mainly associated with increased biomass, kernel number, and harvest index (Sayre et al. 1997). Yield components, such as grain size and number, or harvest index in more recent germplasm, have made relatively little or no contribution in explaining the increases in yield potential. This would mean that selection for increased yield potential and higher kernel weight can proceed simultaneously. Large kernel size continues to be an important trait in local markets of various developing countries and appears to be associated with better emergence under poor management. Some of the recent wheat germplasm developed at CIMMYT has not only shown increased grain yield potential but also kernel weight as high as 60 mg in northwestern Mexico, compared with about 40 mg for most of the wheat germplasm developed during the 1980s and 1990s. Although the early increases in yield potential of semi-dwarf wheat cultivars came from the incorporation of dwarfing genes, subsequent progress can be attributed to additive genes. It is likely that intense breeding efforts during the last three decades in the post-Green Revolution era had already selected for larger effect additive genes. If that is the case, then further progress is expected from selecting genes that have much smaller effects, thus making it necessary to modify the commonly used traditional breeding schemes. We began utilizing a single-backcross crossing approach that was initially aimed at incorporating resistance to rust diseases based on multiple additive, minor genes (Singh and Huerta-Espino

2004). However, it soon became apparent that the single-backcross approach also favored selection of genotypes with higher yield potential. The reason why single backcross shifts the progeny mean toward the higher side is that it favors retaining most of the desired additive genes from the backcross or recurrent parent, while simultaneously allowing the incorporation and selection of additional useful small-effect genes from the donor parent. A selected bulk-breeding scheme was introduced in bread wheat improvement in the mid-1990s. According to Singh et al. (1998b) selection schemes have little or no effect on the performance of progeny lines, the choice of parents determines the progeny response. In all segregating generations until F5 or F6, one spike from each of the selected plants is harvested as bulk and a sample of seed is used in growing the next generation. Individual plants or spikes are harvested in the F5 or F6 generation. This scheme allows retaining a larger sample of selected plants and was found to be highly efficient in terms of operational costs. Moreover, retaining a large sample of plants in segregating populations increases the probability of identifying rare segregates that carry most desired genes. Introgression of new genetic diversity from unrelated wheat germplasm, including inter-specific hybridization, can create a new genetic pool and bring in large or small-effect genes that may not be present in wheat germplasm commonly used in a breeding program. Alien translocation T7DS.7DL7Ae#1L from Thinopyrum elongatum (Host) D.R. Dewey that carries leaf and stem rust resistance genes Lr19 and Sr25, respectively, has been shown to increase yield potential ranging from almost nonsignificant levels to over 15%, depending on genetic background under irrigated conditions through increased biomass production (Singh et al. 1998a) associated with increased spike fertility and photosynthetic rate (Reynolds et al. 2001). Thus, its widespread incorporation is underway and we expect a quantum jump in yield potential in some of the resultant lines.

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Breeding to safeguard wheat crops from important diseases

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One or more of the three rust diseases of wheat continue to pose major breeding challenges worldwide

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due to the pathogens’ ability to evolve continuously, to migrate long distances, and to overcome the deployed race-specific resistance genes. Breeding approaches to control stem rust are described in the below section ‘‘Ug 99 stem rust as a global emerging threat to wheat (food) supply ‘‘ A major genetics and breeding emphasis during the last decades was given to accumulate slow-rusting, minor-resistance genes with additive effects against leaf and yellow-rust pathogens. High diversity exists in CIMMYT spring wheat lines for such genes and new wheat lines that show negligible disease severity at maturity often carry between four and five slow-rusting resistance genes. Recent studies have found that some of the studied slow-rusting resistance genes have pleiotropic effects on multiple diseases. Most known pleiotropic genes are Lr34/Yr18/Pm38/Bdv1 and Lr46/Yr29/Pm39. Past experience deploying cultivars with slow-rusting resistance has shown that such resistance is durable. CIMMYT initiated breeding for resistance to Septoria tritici blotch, caused by Mycosphaerella graminicola (Fuckel) J. Schro¨t. (anamorph Septoria tritici)), in semi-dwarf wheat in early 1970 and steady progress has been made since then. Currently, several high-yielding semi-dwarf wheat lines with good resistance are available. Resistance in these wheat genotypes is derived from diverse sources, including re-synthesized wheat lines. Two high rainfall sites (Toluca and Pa´tzcuaro at Michoacań, Mexico), were used for selection. Some re-synthesized wheat lines developed at CIMMYT have shown excellent resistance that appears to be leading towards immunity to the disease. These sources offer new genetic diversity of resistance originating from durum wheat or Aegilops tauschii Coss. A high level of resistance from original re-synthesized wheat parents was successfully transferred to derived high-yielding lines. Sources of resistance to scab have been divided into three groups: China and Japan, Argentina and Brazil, and Eastern Europe. More recently, additional sources, including some hexaploid-derived lines from re-synthesized wheat parents have also been identified to carry moderate resistance. Earlier genetic analysis indicated that a few additive genes confer resistance in Chinese and Brazilian wheat lines, and genes present in Chinese sources are different from those in Brazilian sources. Although several genomic regions are now known to contribute quantitative

resistance (Anderson et al. 2001; Buerstmayr et al. 2002), a gene from the Chinese cultivar ‘Sumai 3’ in the short arm of chromosome 3B has shown the largest and most consistent effect in reducing disease severity and mycotoxin accumulation (Anderson et al. 2001). Further progress in enhancing the level of resistance beyond the current level can come from a breeding strategy that would favor the accumulation of multiple minor genes from various sources into a single genotype. CIMMYT is pursuing this strategy at present and its outcome will be known in the next 3–4 years. Some of the recent research advances are given below in the section ‘‘Food safety and fighting wheat mycotoxins.’’

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Breeding for water-use efficiency and drought tolerance

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Wheat is increasingly being grown on marginal lands and in farming systems where inputs are limited. In most irrigated areas wheat is grown under insufficient irrigations. More water-efficient or drought-tolerant cultivars can mitigate the effects of changing production environments to some extent. Understanding of the genetic basis of drought tolerance is poor. Nevertheless, considerable progress has been made in yield improvement under drought in recent decades using the wheat gene pool and selecting under drought stress (Trethowan et al. 2002). The opportunity exists to improve the tolerance further if new genetic variability can be combined with existing variability and if the underlying genetic control of tolerance can be better understood. The re-synthesized wheat lines—developed by crossing modern durum wheat with Ae. tauschii, the probable donor of the D-genome in hexaploid wheat—have introduced new genetic variation into the wheat gene pool for many characters. Not surprisingly, re-synthesized wheat lines have also been a source of variation for drought and heat tolerance (Trethowan et al. 2002). Some advanced materials derived from re-synthesized wheat lines have improved adaptation worldwide, especially in drought-stressed environments. To improve the breeding efficiency for drought tolerance, the CIMMYT strategy is to ensure that drought-tolerant germplasm also maintains responsiveness if more moisture becomes available in a season. The high yield potential and tolerance to

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drought stress are not mutually exclusive and can be bred simultaneously by selecting segregating populations under favorable environments and droughtstress environments in alternate generations—a practice used at CIMMYT. Moreover, to generate a more precise drought stress at different growth stages, a drip-irrigation system has been installed to irrigate 17 ha of an experimental field near Ciudad Obregoń, where rainfall during the crop season in most years is negligible. This system allows application of exact amounts of water at chosen growth stages to generate different drought scenarios representing different parts of the world. Drought tolerance is a complex trait that is also influenced by root diseases. Healthier roots use the available soil moisture more efficiently. Fortunately, resistance to nematodes and some root pathogens is often simply inherited and molecular markers are available to assist selection. CIMMYT uses these markers to incorporate resistance in drought-tolerant wheat materials.

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Breeding for heat tolerance

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The genetic control of heat tolerance, like drought tolerance, is poorly understood. Nevertheless, significant variation for heat tolerance exists in the wheat gene pool (Pfeiffer et al. 2005). In many environments, late planting can expose the crop and breeding nurseries to high temperatures from flowering onwards, giving wheat breeders the opportunity to select lines with high levels of heat tolerance. At CIMMYT, lines are selected during the segregating phase for adaptation to heat by planting late. A gravity table is used to separate bulk populations into those that can maintain seed weight under high temperature; the derived lines are then tested under heat stress in yield trials. Physiological tools, such as the infrared thermometer that measures canopy temperature depression (CTD), are also available to assist the plant breeder in discriminating among progenies (Reynolds et al. 1998). Some details on heat screening are also provided in the below section on ‘‘Climate change adaptation and mitigation.’’ Heat avoidance or early maturity is an extremely important trait to circumvent effects of high temperature at grain filling. All popular cultivars currently grown in the eastern Gangetic Plains are earliermaturing than cultivars popular in the northwestern

Gangetic Plains. A simultaneous improvement of heat tolerance and yield potential of earlier-maturing germplasm is the best option to increase production in heat-stress environments and is being practiced (Joshi et al. 2007d).

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Breeding for end-use quality

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Bread wheat is generally milled into flour (both refined and whole meal) and made into leavened breads, flat breads, biscuits, and noodles. The quality of proteins, which have a large effect on end-use quality, is controlled by known high and low molecular weight glutenins and gliadins. A number of rapid, indirect quality tests are available that can be applied in the early generations to increase the probability of identifying progeny with the desired quality profiles. Dough rheological properties can be measured in different ways; some methods are timeconsuming but accurate, e.g., the Alveograph, and others are faster, less expensive, but slightly less accurate, e.g., the Mixograph. Parents for crossing are chosen carefully for quality characteristics. Because the primary objective of CIMMYT’s breeding program is to enhance yield, quality tests are done in advanced generations or after yield testing. A high emphasis is being given to improve the leavened and flat bread quality characteristics. About a third of improved spring wheat materials developed and distributed in recent years have excellent to acceptable leavened and flat bread making characteristics. The section ‘‘Grain quality for adding value in the commodity chain’’ provides further details on this research area.

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Improving winter/facultative and high-latitude wheat

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In the late 1970s and early 1980s CIMMYT researchers realized that winter/facultative wheat breeding for the developing world remained largely un-addressed. Small efforts to breed facultative wheat during the winter cycle in Toluca were primarily based on selection from the germplasm introduced from Eastern Europe and the USA. However, the winter in Toluca was not cold enough for the development of competitive lines. The target region for winter/

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facultative wheat was in the Central and West Asia region covering 15–20 million ha of the crop in Turkey, Iran, Central Asia, and the Caucasus. The early work in Toluca resulted in the identification of good winter parents and some competitive lines that were used mainly for spring 9 winter crosses with Oregon State University. This germplasm was not sufficiently adapted and neither was it on a scale to provide the winter wheat breeding programs in the target region with competitive material. Thus, CIMMYT established a winter/facultative wheat breeding program outside of Mexico and directly in the region. Turkey was chosen due to its diversity of environments and because it is a major winter wheat producer in the region. The agreement signed in 1981 between the Government of Turkey and CIMMYT anticipated the development of new winter/facultative germplasm through a cooperative breeding program. The newly established program operated through several key research institutions in Turkey: the Central Field Crop Research Institute in Ankara, the Anatolian Agric. Research Institute in Eskisehir, and the Bahri Dagdas International Agric. Research Center in Konya—the latter being established specifically to work on winter wheat breeding. The initial breeding efforts were based on screening the large collection of Turkish, East European, and US cultivars and making crosses. At the same time, Spring 9 Winter Program operated at Oregon State University (OSU) by Prof. W. Kronstad, supplied F3–F4 populations originating from crosses between Mexican spring wheat lines and winter wheat lines. The lines selected from introduced germplasm in Toluca were also sent to Turkey. All the populations and lines from CIMMYT and OSU, germplasm from Eastern Europe and the USA were screened in Turkey and the best ones selected for distribution through winter/facultative international nurseries. The Turkey-CIMMYT winter wheat program was joined by ICARDA in 1999 to form the International Winter Wheat Improvement Program (IWWIP). Eventually, Toluca-based winter wheat activities were discontinued. The winter/facultative germplasm presently distributed from Turkey combines the germplasm developed by IWWIP through its breeding program in Turkey and Syria as well as new cultivars and breeding lines from all cooperators who are willing to share germplasm. The programs in Eastern Europe,

the USA, and Central Asia routinely submit the germplasm that goes through a selection procedure and the best material is included for international distribution. This is a specific feature of the winter wheat program that is highly appreciated by the cooperators. Facultative and Winter Wheat Observation Nursery (FAWWON) is distributed globally to over 100 cooperators in 50 countries. Additionally, yield trials are distributed to the target region of Central and West Asia. In retrospective, the establishment of a winter/ facultative breeding program in Turkey was a welljustified move resulting in closing the gap in the provision of germplasm for Central and West Asia. The information on the release of cultivars originating from IWWIP has proved its success in developing germplasm which is well-adapted to the region and competitive with local material. By January 2008, 39 cultivars originating from IWWIP had been released in 10 countries of Central and West Asia, including Afghanistan, Iran, and Turkey. Because these cultivars are competitive in grain yield, they possess higher levels of genetic protection against dominating diseases and especially yellow rust. The genetic diversity of these new cultivars is very broad as their pedigree incorporates not only CIMMYT parents but also a wide range of genetically non-related winter wheat lines from Turkey, Iran, Russia, Ukraine, Romania, Bulgaria, Hungary, and the whole diversity of the US winter wheat. The Turkey-based winter wheat program has now been proven successful both in developing new cultivars as well as in serving as a vehicle for international germplasm exchange and will evolve into a modern program able to efficiently address the upcoming challenges. These are resistance to stem rust, specifically against the Ug99 strain, resistance and tolerance to seed and soil-born pathogens, and bread-making quality, which still needs improvement. These will be enhanced through wider application of double haploids and marker-aided breeding. The fundamental difference between winter and spring wheat breeding at CIMMYT is one generation of breeding per year versus two. This should be compensated by the wider use of modern breeding tools, e.g. doubled-haploids. CIMMYT breeding efforts for high latitude spring wheat were initiated in 1999 in order to address one specific challenge: resistance to leaf rust. The vast

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steppe region of northern Kazakhstan and western Siberia grows around 20 million ha of short season low input wheat in the environment ranging in precipitation from 250 to 450 mm. The cultivars currently grown still represent extensive, tall, and day-length sensitive type. The average yield ranges from 1.3 to 1.8 t ha-1. However, even in the years with sufficient precipitation the response in yield is limited due to widespread occurrence of leaf rust (Morgounov et al. 2007). Essentially, all the major cultivars grown in the region are highly susceptible to the pathogen. The shuttle breeding program between Kazakhstan/Siberia and Mexico had its major objective to incorporate leaf rust resistance while maintaining the broad adaptability and superior bread-making quality. Most crosses are made in Mexico between the Kazakh/Siberian material and the best Mexican lines which are back- or top crossed by Kazakh/Siberian or Canadian parents. The resulting F2 and F3 are screened under leaf rust pressure in the area with extended artificial light to allow selection of day-length sensitive genotypes. The selected F4 and F5 bulks are sent to two key sites in Kazakhstan (Astana) and Siberia (Omsk) for selection under local conditions. The best populations are then distributed to all the breeding programs in the region through the Kazakhstan-Siberia Network for Spring Wheat Improvement (KASIB). By 2008 several batches of germplasm had been sent to the region. It is obvious that the shuttle program managed to reach its objective and there are presently lines in the breeding trials that are competitive in yield while providing good leaf rust resistance. The future of CIMMYT breeding for high latitude regions of Kazakhstan and Siberia may lie in a gradual transfer of its key activities into the region. Mexico, by its geographic position, is not a place to breed for long days. Therefore, special efforts are needed to extend the day length, which is expensive and limits the scale of the breeding. Once the short-term priority of developing the leaf rust resistance is reached—the program may evolve into longer-term efforts of improving grain quality and resistance to Septoria and other pathogens, with most of its activities based in the region and aligned with one of the breeding programs. However, CIMMYT will play a clear role from Mexico, e.g. making crosses and providing valuable parental material.

Broadening the genetic base of, and re-synthesizing wheat with available wild and landrace genetic resources

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Interspecific hybrization, embryo rescue, plant regeneration, cytological diagnostic, breeding methods, stress screening, and the assessment of the stability of the advanced derivatives due to homozygosity, are the tools used by CIMMYT to utilize the wealth of the wheat genetic endowment beyond the cultigen pool (Mujeeb-Kazi and Rajaram 2002). ‘‘Capturing’’ wild grass diversity requires more time and effort for a sequential production from F1s, amphiploids and addition lines to translocation lines. Only translocation lines are useful for wheat breeding, but intermediate products (amphiploids and addition lines) are useful to evaluate the presence of useful genes or traits. Also, certain amphiploids may be propagated as new man-made crops, e.g. triticale (9Triticosecale Witmm. ex. A. Camus—an amphiploid between wheat and rye). The germplasm sources can be classified into three groups (primary, secondary, and tertiary genepools) according to ease of exchanging genetic material with wheat by meiotic recombinations (Jiang et al. 1994). The primary gene pool is the species that have high frequency rates of recombination with wheat, including local landraces, wide forms of tetra and hexaploid wheat, as well as diploid species of A and D genomes. The secondary gene pool consists of species that have less homology and reduced recombination rates such as S (&B) genome species. The tertiary gene pool consists of alien species that have no recombination with wheat chromosomes under normal conditions. They can be useful because they sometimes possess high levels of host plant resistance to biotic stresses, but the most used sources of genetic enhancement for wheat come mainly from the primary gene pool; for example species containing the A and D genomes are sources of alleles that can recombine directly with their respective genome partners in the cultigen pool. Mujeeb-Kazi et al. (1995) gave details of the early years of research at CIMMYT for utilizing wild grass diversity in wheat improvement through interspecific hybridization. CIMMYT has produced F1 hybrids with many genera in Triticeae including Aegilops, Thinopyrum, Secale, Agropyron Gaertn., Elymus L., Leymus Hochst., Hordeum L. and Psathyrostachys

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Nevski. Amphiploids involving Aegilops and Thinopyrum have been used in wheat improvement and those of Secale as new sources in triticale breeding (Mujeeb-Kazi et al. 1995). Addition lines have been also produced from the above materials. Currently, this work focuses on producing translocation lines to supply them to wheat breeders. CIMMYT has been working on capturing genetic sources of the D genome of Ae. tauschii via re-synthesizing hexaploid wheat since 1980s, because of the wide adaptation of the species in many geographical and climate regions (van Slageren 1994). As indicated before, the most widely used approach for re-synthesizing hexaploid wheat includes the use of tetraploid durum and diploid Ae. tauschii. CIMMYT was able to re-synthesize an excess of 1,000 wheat lines with this method. These lines have shown significant and useful diversity that provides better host plant resistance to biotic stresses and for traits that enhanced adaptation to abiotic stress-prone environments. Figure 3 shows the increased recent use by CIMMYT of wild species genetic endowment in wheat breeding for rainfed environments through the use of re-synthesized wheat. The re-synthesized wheat-derived lines extract more water from deeper soil profiles (Reynolds et al. 2007). Such ability under drought stress may account for the yield advantage of the re-synthesized wheat derivatives vis-a`-vis their recurrent parents (R. Trethowan, Univ. of Sydney, Australia, personal communication). The re-synthesized wheat lines were also used in CIMMYT as new sources to breed host plant resistance to Karnal bunt (Tilletia indica Mit.) and Helminthosporium leaf blight (Cochliobolus sativus (S. Ito & Kurib.) Drechsler ex Dastur) (Mujeeb-Kazi et al. 2001a, b). CIMMYT continues exploiting re-synthesized hexaploid wheat lines following the crossing scheme shown in Fig. 3 but has also started developing re-synthesized wheat based on wild tetraploid species. A better understanding of wheat evolution provides for enhancing the ‘‘capture’’ of new diversity through re-synthesis—the first step of an evolutionary breeding strategy for wheat improvement that broadens the genetic base of the cultigen pool. In this regard, Warburton et al. (2006) assessed the change in latent genetic diversity of CIMMYT released germplasm over time to determine the effect of selection, and more recent attempts to broaden the germplasm base of CIMMYT wheat lines. The study

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Fig. 3 Percentage of crosses with re-synthesized wheat the parental pedigrees in CIMMYT wheat breeding project for rain-fed environments in the last decade

used simple sequence repeats (SSR) markers to measure the molecular diversity in CIMMYT and CIMMYT derived-wheat lines over time; to compare this diversity to that of the landraces they replaced; and in particular to assess the effects of newly re-synthesized-derived wheat germplasm on the diversity levels of CIMMYT wheat lines. The data presented by Warburton et al. (2006) for the period from the mid twentieth century to its conclusion, indicate an initial drop in inherent diversity from the level measured in landraces, followed by a period of equilibrium. This is understandable as increasingly diverse bread wheat cultivars from around the world were introduced into the CIMMYT crossing programs, while at the same time fixed lines were selected that required very precise adaptation to specific wheat growing environments around the globe, particularly in developing countries. During this process, the use of host plant resistance mitigated the effects of some diseases, nevertheless new pathogens or biotypes would find a relatively uniform genome in the host crop as a result of earlier narrowing of genetic diversity. However, the use of re-synthesized hexaploid wheat lines in crosses during the past 10 years has dramatically altered the balance of genetic diversity. The inherent diversity of the new re-synthesized derivatives is comparable to that of the landraces; however, they express improved yield, host plant resistance, abiotic stress tolerance and in some cases even better end-use quality.

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The quest for wheat yield potential

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It is clear that the periods from 1951 to 1962 (adoption of improved non-semi-dwarf cultivars) and

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from 1963 to 1975 (the celebrated period of the introduction and adoption of reliable semi-dwarf cultivars) were both eras of remarkable increase in wheat yields in farmer fields (Table 6). Just as the impact of the Green Revolution can be attributed mostly to improved partitioning of the products of photosynthesis to grain yield, progress in yield of irrigated wheat since the development of semi-dwarf lines, as pointed out by Sayre et al. (1997), is also most strongly associated with improved harvest index (HI). However, from 1976 to 2005 it was noted a comparably large decrease in the rate of yield increase in farmer fields to about 1% year-1, a rather disturbing observation. There are several reasons, which are related to both breeding as well as crop management issues. Previous studies in the Yaqui Valley have concluded that about 50% of farmer wheat yield increases have been associated with genetic improvements in yield potential and 50% has been associated with improved crop-management practices, e.g. higher fertilizer rates, better irrigation management, and the use of bed planting systems (Bell et al. 1995; Sayre et al. 1997). The rate of increase in bread and durum wheat genetic yield potential was high for cultivars bred from the mid-1960s to the mid-1980s but has subsequently declined over the past 10 years. However, under conditions where pests (rusts in particular) are not controlled, yield potential for both bread and durum wheat—bred until the 1990s, showed increases reflecting the investment made in breeding for potential durable host plant resistance to rusts. Unlike the Green Revolution cultivars that relied on single gene rust resistance—which can easily be eroded as new pathogen races evolve, more modern cultivars have multi-gene resistance that can be expected to stand the test of time (Sayre et al. 1998). Wheat improvement at CIMMYT expanded the genetic base of modern wheat lines using conventional breeding as well as cytogenetic-led approaches for introgressing alleles from wild relatives. For example, the highly successful ‘Veery’ lines bred in the early 1980s ensued from the cross of a winter wheat parent containing the 1B/R rye translocation. Approximately 3,170 different crosses were made among 51 individual parents originating in 26 countries around the world to develop the Veery lines, of which 62 of them were grown annually on about 3 million ha from Chile to China. These widely

adapted Veery lines had an outstanding yield potential and other interesting physiological traits, e.g. the cultivar ‘Seri 82’showed superior leaf photosynthetic rate, stomatal conductance, and leaf greenness relative to a set of hallmark varieties developed both before and after its release (Fischer et al. 1998). The success of lines possessing the chromosome substitution T1BL.1RS may also be related to increased tolerance to stresses (Villarreal et al. 1997). Last but not least, the use of winter 9 spring crosses for wheat improvement at CIMMYT, which began in the early 1970s, contributed to increasing the genetic diversity of the spring wheat gene pool. CIMMYT ideotype research using modem semidwarf spring wheat cultivars, representing a range of yield potential, supports the idea that genes conferring yield, through improved adaptation to the crop environment, are associated with a less competitive phenotype (Reynolds et al. 1994a). One important implication of these results is that improvement in yield potential would appear to be more a function of improved adaptation to canopy microenvironment, rather than macro-environmental factors such as climate. Reynolds et al. (1999) reviewed the physiological and genetic changes in irrigated wheat in the post-Green Revolution period. Their assessment shows that morphological traits associated with increased yield potential in CIMMYT-derived wheat cultivars released between 1962 and 1988 include grain number and HI (Reynolds et al. 1999). Although increased HI seems to account for improvements in genetic yield potential, even in the aftermath of the Green Revolution, it should be taken into account with caution due to theoretical limit to HI, estimated at 60% (Austin et al. 1980), e.g. if HI could be raised to 60% from its current maximum value (approximately 50%), it implies that grain yields could only be increased by a further 20% using HI as a selection criterion, unless total crop biomass is also raised. As indicated previously, significant increase in yield and biomass has been observed in several backgrounds when alien chromatin associated with Lr19 was introgressed from Th. elongatum (Reynolds et al. 2001). Lr19—transferred to wheat through the 7DL.7Ag translocation—was associated with increases in yield (average 13%), final biomass (10%), and grain number (15%) in all backgrounds

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studied. Lrl9 was associated with an increased partitioning of biomass to spike growth at anthesis (13%), a higher grain number per spike, higher radiation-use efficiency and flag-leaf photosynthetic rate during grain filling (Reynolds et al. 2005). The hypothesis that photosynthesis and RUE may respond directly to a larger number of grains per spike was tested experimentally by imposing a light treatment during boot stage. The treatment was associated with a small increase (5%) in the proportion of biomass invested in spike mass at anthesis, reflected by on average three extra grains per spike at maturity. The treatment was associated with 25% more yield and 22% more biomass than checks, while carbon assimilation rate measured on flag-leaves during grain-filling was 10% higher than checks. The results suggest that RUE can be increased indirectly by increasing sink strength and a major yield-limiting factor in modern high-yielding spring wheat is still the determination of kernel number (Reynolds et al. 2005). This research illustrates the advantage of introgressing wild relatives’ genes for improving grain yield potential in wheat.

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The power of in silico breeding to define wheat genetic enhancement approaches

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The strategies used by CIMMYT breeders have evolved. Pedigree selection was used primarily from 1944 until 1985. From 1985 until the second half of the 1990s the main selection method was a modified pedigree/bulk method (MODPED) (van Ginkel et al. 2002), which successfully produced many of the widely adapted wheat cultivars now being grown in the developing world. This method was replaced in the late 1990s by the selected bulk method (SELBLK) (van Ginkel et al. 2002) in an attempt to improve resource-use efficiency. The major differences between MODPED and SELBLK are outlined below. The MODPED method begins with pedigree selection of individual plants in the F2 generation followed by three bulk selections from F3 to F5, and pedigree selection in the F6; hence the name modified pedigree/bulk. In the SELBLK method, spikes of selected F2 plants within one cross are harvested in bulk and threshed together, resulting in one F3 seed lot per cross. This selected bulk selection is also used

from F3 to F5, while pedigree selection is used only in the F6. A major advantage of SELBLK compared with MODPED is that fewer seed lots need to be harvested, threshed, and visually selected for seed appearance. In addition, significant savings in time, labor, and costs associated with nursery preparation, planting, and plot labeling ensue, and potential sources of error are avoided (van Ginkel et al. 2002). Although some small-scale field experiments have been conducted comparing the efficiencies of CIMMYT wheat breeding methods (Singh et al. 1998b), the efficiency of SELBLK, compared with that of MODPED, remained untested on a larger scale until the use of the breeding simulation tool of QuLine.

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The breeding and simulation tool of quLine

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QU-GENE is a simulation platform for quantitative analysis of genetic models, which consists of a twostage architecture (Podlich and Cooper 1998). The first stage is the engine (referred to as QUGENE), and its role is to define the genotype 9 environment (GE) system (i.e., all the genetic and environmental information of the simulation experiment), and generate the starting population of individuals (base germplasm). The second stage encompasses the application modules, whose role is to investigate, analyze, or manipulate the starting population of individuals within the GE system defined by the engine. The application module will usually represent the operation of a breeding program. A QU-GENE strategic application module, QuLine, has therefore been developed to simulate the breeding procedure for deriving inbred lines. Built on QU-GENE, QuLine (previously called QuCim) is a genetics and breeding simulation tool that can integrate various genes with multiple alleles operating within epistatic networks and differentially interacting with the environment interaction, and predict the outcomes from a specific cross following the application of a real selection scheme (Wang et al. 2003; Wang et al. 2004). It therefore has the potential to provide a bridge between the vast amount of biological data and breeders’ queries on optimizing selection gain and efficiency. QuLine has been used to compare two selection strategies (Wang et al. 2003), to study the effects on selection of dominance and epistasis (Wang et al. 2004), to predict cross performance using known gene information (Wang et al. 2005),

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and to optimize marker-assisted selection to efficient pyramid multiple genes (Kuchel et al. 2005; Wang et al. 2007a, b; Ye et al. 2007).

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Comparison of breeding efficiencies for different selection strategies through simulation

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The genetic models developed have accounted for epistasis, pleiotropy, and genotype-by-environment interaction. The simulation experiment comprised the same 1,000 crosses, developed from 200 parents, for both breeding strategies. A total of 258 advanced lines remained following 10 generations of selection. The two strategies were each applied 500 times on 12 GE systems.

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Genetic gain in yield from MODPED and SELBLK

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The average adjusted gains were 6.7 t ha-1 for no epistasis, 5.4 t ha-1 for di-genic epistasis, and 5.7 t ha-1 for tri-genic epistasis, which indicates that epistasis will reduce the adjusted gain. The adjusted gain associated with the absence of pleiotropy is also higher than that for the presence of pleiotropy. These results suggest that the increase in gene number and the presence of epistasis and pleiotropy make it more difficult for a breeding strategy to identify the trait performance level of the best genotype in the defined GE system. When the experimental factors are considered individually, the adjusted gain from SELBLK is always significantly higher than that from MODPED, except in the absence of pleiotropy, indicating SELBLK is at least equivalent to or better than MODPED. The average adjusted genetic gain on yield is 5.8 t ha-1 for MODPED and 6 t ha-1 for SELBLK, a difference of 3.3% (Fig. 4a). This difference is not large and therefore unlikely to be detected using field experiments (Singh et al. 1998b). However, it can be detected through simulation, which indicates that the high level of replication (50 models by 10 runs in this experiment) possible using simulations can better account for the stochastic properties of a run of a breeding strategy and for the sources of experimental errors. The average adjusted gains for the two yield gene numbers 20 and 40 are 6.83 and 5.02, respectively, suggesting that genetic gain decreases with increasing yield gene number.

Number of crosses remaining after selection

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The same 1,000 crosses were made for both breeding strategies and 258 advanced lines were selected after a breeding cycle, regardless of the GE system used. The number of crosses remaining after one breeding cycle is significantly different among models and strategies, but not among runs. The number of crosses remaining from SELBLK is always higher than that from MODPED, which means that delaying pedigree selection favors diversity. On average, 30 more crosses were maintained in SELBLK (Fig. 4b). However, there is a crossover between the two breeding strategies (Fig. 4b). Prior to F5 the number of crosses in MODPED is higher than that in SELBLK. The number of crosses becomes smaller in MODPED after F5 when pedigree selection is applied in F6. Among-family selection from F1 to F5 in SELBLK is equal to among-cross selection, and results in a greater reduction in cross number for SELBLK compared to MODPED in the early generations. In general, only a small proportion of crosses remain at the end of a breeding cycle (11.8% for MODPED and 14.8% for SELBLK); therefore, intense among-cross selection in early generations is unlikely to reduce the genetic gain. On the contrary, breeders will tend to concentrate on fewer but ‘‘higher-probability’’ crosses. That just a few crosses of the many generated remain after the final yield trial stage is common in most breeding programs. Since more crosses remain in SELBLK, the population following selection from SELBLK may have larger genetic diversity than that from MODPED. In this context, SELBLK is also superior to MODPED.

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Resource allocation

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Since the number of families and selection methods after F8 are basically the same for both MODPED and SELBLK, only the resources allocated from F1 to F8 are compared. The total number of individual plants from F1 to F8 was calculated to be 5,155,090 for MODPED and 3,358,255 for SELBLK (Fig. 4c). Assuming that planting intensity is similar, SELBLK will use approximately two thirds of the land allocated to MODPED. Furthermore, SELBLK produces a smaller number of families compared to MODPED (Fig. 4d). From F1 to F8, there are 63,188

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Fig. 4 Results from the simulation experiment (adapted with modifications from Fig. 2 of Wang et al. (2003)). (a) Adjusted genetic gain after one breeding cycle across all experimental sets; (b) Number of crosses after each generation’s selection across all experimental sets; (c) Number of individual plants in each generation in one breeding cycle; (d) Number of families in each generation in one breeding cycle. F8(T), F8 field test in

Toluca; F8 (B), F8 field test in El Batan; F8 (YT), F8 yield trial in Ciudad Obregon; F8(SP), F8 small plot evaluation in Ciudad Obregon; F9(T), F9 field test in Toluca; F9(B), F9 field test in El Batan; F9(YT), F9 yield trial in Ciudad Obregon; F9(SP), F9 small plot evaluation in Ciudad Obregon; F10(YR), F10 stripe rust screening in Toluca; F10(LR), F10 leaf rust screening in El Batan

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families for MODPED but only 24,260 for SELBLK, approximately 40% of the number for MODPED. Therefore when SELBLK is used, fewer seed lots need to be handled at both harvest and sowing, resulting in significant savings in time, labor, and cost.

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Further use of in silico-aided genetic enhancement

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QuLine is a QU-GENE application module that was specifically developed to simulate CIMMYT’s wheat breeding programs, but with the potential to simulate most, if not all, breeding programs for developing inbred lines. The breeding methods that can be simulated in QuLine include mass selection, pedigree breeding (including single seed descent), bulk population breeding, backcross breeding, top cross (or three-way cross) breeding, doubled haploid breeding,

marker-assisted selection, and combinations and modifications of these methods. The chromosomal locations of genes and markers, and their occurrence in specific parents can be explicitly and precisely defined (Wang et al. 2003). Simulation experiments can therefore be designed to compare the breeding efficiencies of different selection strategies under a series of pre-determined genetic models. A great amount of studies on quantitative trait loci (QTL) mapping have been conducted for various traits in plants and animals in the last 10 years (Dwivedi et al. 2007 and references therein). However, QTL discovery and cultivar development in most cases are two separate processes. How QTL mapping results can be used to pyramid desired alleles at various loci has rarely been addressed in the literature. As the number of published genes and QTL for various traits continues to increase, the challenge for plant breeders is to determine how to best utilize



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this multitude of information in the improvement of crop performance. QuLine provide an appropriate tool that can combine different types and levels of biological data such that the complex and voluminous data is turned into knowledge that can be applied in breeding.

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Information management and knowledge sharing: the wheat phenome atlas

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A useful new tool for crop genetic improvement is association analysis (AA), which is the direct selection of polymorphic markers associated with phenotypic variation for important traits and identified by the linkage disequilibrium (LD) between loci (Thornsberry et al. 2001; Flint-Garcia et al. 2003). This LD is determined by their physical distance across chromosomes and has proven to be useful for dissecting complex traits because it offers a fine scale mapping due to historical recombination (Lynch and Walsh 1998). However, covariance between markers and traits not due to physical distance can arise due to population structure caused by admixture, mating system, and genetic drift, or by artificial or natural selection during evolution, domestication, or plant improvement. These factors create subpopulation structure in a linkage disequilibrium study, which leads to LD between loci that are not physically linked and cause a high rate of false positives when relating polymorphic marker to phenotypic trait variation. However, LD due to physical linkage can be differentiated from LD due to population structure using statistical methods such as those suggested by Pritchard et al. (2000) and Yu et al. (2006). In addition to controlling population structure, successful application of AA requires comprehensive phenotypic data, including replicated field trials for modeling GE interaction. An advantage of AA is that large amounts of historical phenotypic data can be used, as demonstrated by Crossa et al. (2007). This can decrease the need for additional, expensive and time consuming phenotyping. CIMMYT, Cornell Univ (Ithaca, NY, USA), and the Univ. of Queensland (Brisbane, Australia) recently launched the Wheat Phenome Atlas initiative which aims for enabling technologies to link genotype to phenotype across a wide range of agronomic traits of high priority to wheat farmers across the

world. The Wheat Phenome Atlas will facilitate more rapid development of molecular breeding tools, increased understanding of genotype-by-environment interaction, and will lead to increased precision and scope of targeted breeding impacts. The Phenome Atlas Toolbox will be developed as an open source resource for wheat genetics, breeding, pathology, physiology, and biological research. The initiative is based on a unique database (amongst crop plants) developed by CIMMYT and national partners over the past half century, based on the field evaluation of more than 15,000 elite breeding lines in more than 100 locations across the world—at a cost of about US$ 0.5 billion. All seed from these breeding lines has been preserved in the CIMMYT germplasm bank and can now be subjected to whole genome genotyping. The proof-of-concept in this area was recently carried out by researchers from the CIMMYT Crop Research Informatics Laboratory (an initiative of the CIMMYT-IRRI Alliance), the University of Queensland, and Cornell University with the biotech company Triticarte, who have developed the high throughput genotyping protocol—diversity array technology or DArT for short (Crossa et al. 2007). The Wheat Phenome Atlas initiative is based around the ICIS (International Crop Information System), an open-source informatics platform used by CGIAR, NARS, and private sector germplasm banks, researchers, and breeders across the world. All data and resources developed through this initiative will be available to wheat researchers and breeders across the world through public access databases and portals. It is envisaged that additional international collaborators will join the initiative, including advanced research institutes from the USA, Europe, and Australasia, strong NARS from Latin America and Asia, plus private sector breeding companies from across the world. Establishing the analytical tools to deal with data sets of over 15,000 lines 9 40 years 9 80 traits 9 100 locations 9 2,000 DNA data points (approximately 10 billion data points) will involve the development of new and powerful bioinformatics tools and webpage visualization software. The Phenome Atlas Toolbox will facilitate the identification of gene blocks having beneficial effects on high priority agronomic traits such as rust resistance, drought tolerance, and yield. From these outputs it

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will be possible to develop molecular tools for rapidly introgressing these elite gene blocks into new cultivars. The Wheat Phenome Atlas database will also be used for modeling and simulation studies to predict cultivar performance in a range of global environments, including future environments predicted by climate change models (CIMMYT 2007). It is envisaged that the Phenome Atlas Toolbox will develop dynamically with input from wheat researchers worldwide. The Phenome Atlas Toolbox will be generic and applicable to all biological systems, whether plant or animal.

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Safe and legal movement of wheat germplasm worldwide

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CIMMYT has a global mandate for the improvement of wheat and maize and it has also the responsibility of conserving the germplasm of these crops. CIMMYT’s germplasm improvement programs rely heavily on the free international exchange of maize and wheat seed. All concerned institutions, cooperators, and regulating authorities must have confidence in the safety of both imported and exported seed to facilitate such exchange. CIMMYT is fully committed to maintaining fundamental health standards in its worldwide operations. These standards are dictated at different levels by the International Plant Protection Convention (FAO 1997 https://www.ippc.int/IPP/En/ default.jsp), by IT-PGRFA (FAO 2002), and by the CGIAR (1999). CIMMYT policies and practices and its Seed Health Laboratory (SHL) control and ensure the implementation of international and national phytosanitary regulations for material that is distributed every year. CIMMYT SHL has operated since 1998 under the approval of the Mexican Ministry of Agriculture (SAGARPA) (Norma Oficial Mexicana 036-FITO1995), and since April 2007 with the accreditation under norm ISO/IEC NMX-EC-17025-IMNC-2005 General Requirements for the Competence of Testing and Calibration Laboratories. These essential legal recognitions guarantee to the Mexican phytosanitary authorities that CIMMYT seed exchange activities do not jeopardize the internal Mexican or international phytosanitary situation and that the quarantine procedure carried out on seed introductions strictly adheres to Mexican phytosanitary regulations. Likewise, they

reassure our collaborators that CIMMYT procedures are standardized, internationally recognized, and controlled constantly through internal and external audit processes. The principal functions of CIMMYT SHL are to: certify the viability and health of maize and small grain cereal seed for international shipments, control the safety of seed arriving to CIMMYT and apply Mexican quarantine regulations, detect the unintentional presence of transgenes on maize introductions from risky countries, maintain the relationship with, and act as spokesman with Mexican phytosanitary authorities, supervise the seed-treating procedures, inspect field multiplication and introduction plots, and ensure that chemical prophylaxes against quarantine disease are applied in the multiplication plots, in storehouses, and in seed preparation areas. The SHL represents the point of entry and exit of all seed shipments to and from CIMMYT headquarters. Seed samples are delivered by programs for analyses or are received from collaborators; upon completion of the testing process the seed is ‘‘released’’ and ready to be shipped abroad or planted in CIMMYT experimental stations. According to Mexican phytosanitary regulations, when the interception of a pathogen of quarantine importance occurs both on outgoing or incoming material, the SHL must inform Mexican phytosanitary authorities, who will indicate the measures to follow to prevent the spread of the pathogen. During 2007 the SHL carried out quarantine procedures on 62 seed introductions of small grain cereals (wheat, triticale, and barley) proceeding from 20 countries and analyzed 822 samples. From this number of samples, which included 41,257 seeds, two interceptions of the quarantined pathogen Tilletia indica were made on two seed introductions that were incinerated. Karnal bunt is considered a disease of moderate economic importance (CABI 2005), for example in Mexico, where Karnal bunt appears regularly, direct losses are not very significant and do not exceed 1%. However, the indirect costs to the Mexican economy are more significant due to quarantine measures, which have to be applied for grain exports (Brennan et al. 1992). The same happens in the USA (Rush et al. 2005). In Europe and Australia the disease is still considered a high risk (Bartlett 2000; Murray and

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Brennan 1998), in spite of the strict environmental requirement that the pathogen has for developing and affecting wheat and triticale (Jones 2007). The disease is given political recognition in many countries. In terms of its phytosanitary importance, the pathogen is quarantined in more then 40 countries in the world (Rush et al. 2005). Hence, CIMMYT is obligated to devote a considerable amount of resources in applying a zero-tolerance policy against this disease. Besides T. indica, particular care is also taken by CIMMYT to prevent infections by Xanthomanas translucens (Jones et al.) Vauterin et al. pv. undulosa, the Barley Stripe Mosaic virus, and the Wheat Streak Mosaic virus through inspection of the seed before and after planting. In the case of outgoing germplasm, 2,468 samples were tested at the SHL before the shipments were sent in 2007. The phytosanitary quality of outgoing seed is particularly high due to the procedure followed in the multiplication plots that are planted in an internationally recognized Karnal bunt free area in northwest Mexico and that are submitted to a prophylaxis against Karnal bunt and other foliar diseases, which includes 3–4 fungicide treatments with propiconazole and tebuconazole during the cropping cycle and insecticide to protect the crop from aphid- and mite-borne viruses. Therefore, the range of pathogens detected on the seed mainly consists of saprophytes or minor seed-borne pathogens that do not affect seed quality, such as fungi

belonging to the genus Alternaria, Cephalosporium, Fusarium, Bipolaris, Curvularia, and Cladosporium. Starting 1 January 2007, the CGIAR Centers had to use the Standard Material Transfer Agreement (SMTA) for all shipments, which was adopted in the first session of the Governing Body of the IT-PGFRA. It was agreed upon through the Statement of the CGIAR Centers regarding Implementation of the Agreements between the Centers and the governing body of the International Treaty on Plant Genetic Resources for Food and Agriculture. CIMMYT started using the SMTA as of 14 January 2007, but did not distribute any material prior to that date. During 2007, 565 shipments were sent under the SMTA and three were rejected. Table 7 provides a summary of the number of international nursery seed sets sent during 2007 from CIMMYT headquarters. This table includes bread, durum wheat, triticale, and barley. The seed is distributed mainly to governmental research institutions and national programs in Asia and Central and West Asia and Northern Africa (CWANA) through the CIMMYT International Wheat and Improvement Network that every year makes available 14 nurseries adapted to different environments. Table 8 provides a list of nurseries available and whose seeds can be requested by any party that agrees with the SMTA which regulates the use and benefit sharing of the germplasm according to the IT-PGRFA. This activity constitutes the backbone of the breeders’ research

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Table 7 Number of international nurseries sets of small grain cereals (wheat, barley and triticale) sent by CIMMYT during 2007 to different regions 2007

Region Africa Asia Caribbean CWANAa Europe North America Oceania

Barley

Bread wheat

Durum wheat

Special nurseries

Triticale

1

Total by region

24

85

10

12

132

47

205

41

16

309

133

325

123

52

633

19

110

46

30

205

21

113

27

19

181

1

4

2

1

2

1

2

South America

30

119

27

3

28

207

Total by crop

277

957

276

5

158

1,673

a

CWANA: Central/West Asia and North Africa, which include Algeria, Egypt, Ethiopia, Eritrea, Libya, Mauritania, Morocco, Sudan and Tunisia (North Africa and Nile Valley), Bahrain Iraq, Jordan, Kuwait, Lebanon, Palestine, Qatar, Saudi Arabia, the Sultanate of Oman, Syria, Turkey, the United Arab Emirates and Yemen (Middle East), Afghanistan, Armenia, Azerbaijan, Georgia, Iran, Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan and Uzbekistan (Central Asia and Caucasus)



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Name of the nursery

Crop

Elite Spring Wheat Yield Trial

Spring bread wheat

Semi-Arid Wheat Yield Trial

Spring bread wheat

High-Rainfall Wheat Yield Trial

Spring bread wheat

International Bread Wheat Screening Nursery

Spring bread wheat

Semi-Arid Wheat Screening Nursery

Spring bread wheat

High-Rainfall Wheat Screening Nursery

Spring bread wheat

High-Latitude Wheat Screening Nursery

Spring bread wheat

(Fusarium) Scab Resistance Screening Nursery Stem Rust Resistance Screening Nursery

Spring bread wheat Bread wheat

International Durum Yield Nursery

Durum wheat

International Durum Screening Nursery International Triticale Yield Nursery International Triticale Screening Nursery International Barley Yield Trial z a

Durum wheat Triticale Triticale Barley

International Barley Observation Nurserya

Barley

Early Maturity Barley Screening Nurserya

Barley

Hull-less Barley Screening Nursery

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ICARDA-CIMMYT Barley program, distributed only until 2007

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Table 8 Name of the nurseries distributed from Mexico by CIMMYT every year to the International Wheat Improvement Network

Barley

Table 9 Number of small grain cereals lines distributed as miscellaneous shipment during 2007 to different regions in the world Region Africa Asia Caribbean Europe Middle Easta North America Oceania South America Total by crop a

Bread wheat

Durum wheat

Triticale

Barley

Genebank

12,138

4,953

8,548

503

6 672

3 984

Total by region

430

415

132

18,068

198

304

717

10,270

47

1 21

716

10 2,440

1,485

52

27

61

1,238

2,863

1,766

13

12

1,460

17,735

20,986

3,267

546

33

1

28

3,875

5,006

6

28

2,679

1,185

8,924

32,888

7,080

775

4,942

21,751

67,436

Bahrain, Iraq, Jordan, Kuwait, Lebanon, Palestine, Qatar, Saudi Arabia, the Sultanate of Oman, Syria, Turkey, the United Arab Emirates and Yemen

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programs due to the valuable information sent back by the collaborators that feeds into the breeding program. Such feedback allows for a constant and prompt improvement of wheat germplasm according to the users’ needs and to the biotic and abiotic stresses that threaten wheat production in developing countries. CIMMYT also distributes a great number of lines that are developed under specific projects between CIMMYT and several collaborators in the public and private sector. These are called miscellaneous shipments and as it is shown in Table 9 the greatest part is sent to Africa, Asia, and North America. Miscellaneous shipments include also germplasm

requested by genebanks to absolve specific scientific needs and also for conservation of duplicates in other genebanks.

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International CIMMYT wheat nursery systems

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CIMMYT-improved germplasm is dispatched through nurseries targeted to specific spring and winter type, irrigated, high-rainfall, semi-arid, and heat-tolerant requiring agro-ecological environments to a network of wheat researchers worldwide (http://www.cimmyt.org/ english/wps/obtain_seed/frmrequesttrialswheat.htm).

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In exchange, they provide the data from their trials to CIMMYT for further cataloging and analysis. The use of the international trial data assists in the improvement of wheat breeding approaches by CIMMYT. For example, this information has proven useful for establishing associations among stress environments and irrigation systems in the screening fields at CIMMYT’s main wheat breeding sites in Mexico (Ciudad Obregoń, Toluca, and El Batań), and international test sites for spring bread wheat. Two basic types of nurseries are distributed, yield trials containing 30–50 of the best selected advanced lines and materials nominated by national program partners; and, screening nurseries containing up to 200 advanced lines selected for specific targeted traits and elite genetic diversity. Nurseries are distributed for spring bread wheat, spring durum wheat, spring and facultative triticale by CIMMYT from Mexico (Table 8), and winter and facultative bread wheat from the Turkey/CIMMYT/ICARDA cooperative program. Full pedigree and respective selection history are known for each line and their phenotypic data cover yield, agronomic, pathological, and quality traits. Appropriate data analysis for CIMMYT nurseries tested worldwide or regionally help to understand genotype-by-environment interactions (GEI), broad and specific adaptation and their influence on grain yield and other traits (Ortiz et al. 2007c and references therein). The recoding of environmental factors, host plant resistance to biotic stresses and adaptation to abiotic stresses provides additional means to account for the GEI. Such information coupled with an enhanced knowledge regarding the adaptation and stability of wheat breeding lines allows a better targeting of bred-germplasm to specific environments, particularly in stress-prone areas where reducing the risk of crop failure and better use of inputs are needed to ensure maximum performance.

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Wheat genetic resources enhancement addressing global challenges

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As the world food situation is being transformed by new driving forces (von Braun 2007), wheat farmers and researchers are confronted with major challenges but also emerging opportunities. It may be that the ‘‘easy gains’’ from wheat research have been

exhausted. Clearly, past impacts from wheat research have been greater in high input farming systems, where semi-dwarf cultivars responded well to the increased use of fertilizers and irrigation. Later, spillovers accumulated as improved cultivars spread from irrigated to higher potential rainfed areas, and then progressively into lower potential rainfed areas (Dixon et al. 2006). Looking to the future, will changing consumer preferences and strengthening market value chains create adequate new markets for quality wheat that will justify increased attention to breeding for quality? Will molecular breeding improve the efficiency of field breeding and accelerate the release of dramatically more productive lines and cultivars? Does genetically-modified (GM) wheat have significant potential benefits for the industry and consumers? Will the impact of global climate change require major shifts in wheat research and breeding objectives? Are there improved soil and crop management technologies which would enable farmers to obtain the full benefit of new wheat cultivars, while conserving the resource base for future generations of wheat farmers? Are there proven models of integrated ‘‘germplasm enhancement—improved crop management—or more favorable policy environment’’ approaches that might be replicated in major wheatproducing areas?

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Climate change adaptation and mitigation

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Climate change could strongly affect the wheat crop that accounts for 21% of food and 200 million ha of farmland worldwide (Ortiz et al. 2008b). The InterGovernmental Panel on Climate Change (2001) already concluded that ‘‘the model of cereal crops indicated that in some temperate areas potential yields increase with small increases in temperatures but decrease with larger temperature changes’’. As a result of possible climate shifts in the Indo-Gangetic Plains—currently part of the favorable, high potential, irrigated, low rainfall mega-environment, which accounts for 15% of global wheat production—as much as 51% of its area might be reclassified as a heat-stressed, irrigated, short-season production mega-environment (Hodson and White 2007). This shift would also represent a significant reduction in wheat yields, unless appropriate cultivars and crop management practices were offered to and adopted by South Asian farmers.

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To adapt and mitigate the climate change effects on wheat, supplies for the poor, heat-tolerant wheat germplasm should be bred. Likewise, wild relatives of wheat as potential sources of genes with inhibitory effects on soil nitrification must be assessed.

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Adaptation to heat and water stresses

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Wheat yield in most tropical and subtropical locations will decrease due to global warming, which may be further affected by water scarcity or drought (Ortiz et al. 2007c). Drought and heat are therefore key factors with high potential impacts on crop yield (Barnabas et al. 2008) One approach to solve these heat- and water-related constraints is improving wheat germplasm with higher tolerance to stresses associated with these environments. Hence, wheat breeders should start genetically enhancing the crop to maintain yield under higher temperatures or water scarcity using all available means in the tool kit. Recognizing water productivity and water-use efficiency as priorities for wheat, CIMMYT researchers disaggregated grain yield under water stress into distinct components to apply these findings to the genetic enhancement of this crop (Reynolds and Borlaug 2006). Ongoing research is providing a better understanding of traits with major effects on water productivity in dry land wheat areas (Reynolds et al. 2007). These include root architecture and physiological traits, resistance to soil-borne pests and diseases, tolerance to heat and salinity, and zincdeficient and boron toxic soils. The combination of improved germplasm, the Center and partners’ expertise in drought physiology, soil-borne diseases, agronomy, and the availability of DNA markers for various traits place CIMMYT in a unique position to develop water-productive wheat with resistance to the important stresses for use by partners throughout the developing world. Some important attributes for drought-prone environments are available in the wild relatives of wheat (Reynolds et al. 2007). Re-synthesizing hexaploid wheat with wild ancestors has been used at CIMMYT for tapping this useful variation and incorporating such genetic resources into wheat-bred germplasm (Dreccer et al. 2007). Recently, Ogbonnaya et al. (2007) found that such lines deriving from re-synthesizing wheat yielded 8–30% higher than the best local check in multi-site trials across diverse regions of

Australia. Their results reinforce previous research conducted at CIMMYT that lines derived from synthetic wheat have the potential to significantly improve grain yield across environments. In addition to the above undertakings, transgenic approaches for incorporating stress-inducible regulatory genes that encode proteins such as transcription factors (e.g. DREB1A) into the wheat cultigen pool are also being pursued (Hoisington and Ortiz 2008). The DREB1A gene was placed under the control of a stress-inducible promoter rd29A from Arabidopsis rd29A gene and inserted via biolistic approach into bread wheat (Pellegrineschi et al. 2004). Plants expressing the DREB1A gene demonstrated substantial resistance to water stress in comparison with checks under experimental greenhouse conditions manifested by a 10-day delay in wilting when water was withheld. Severe symptoms (death of all leaf tissue) were evident in the controls after 15 days without water. The transgenic wheat lines started to show water-stress symptoms only after 15 days. The greenhouse pot experiments based on severe desiccation stress do not however represent typical field conditions and, therefore, the plants may not be exhibiting a response that would be valuable in farmers’ fields. Hence, CIMMYT researchers shifted their attention to evaluating transgenic wheat lines in contained field trials. Preliminary results showed that the DREB1A gene in wheat significantly lowers canopy temperature compared with the control in these trials mimicking unpredictable mid-season (vegetative phase) drought (Ortiz et al. 2007a). The gene DREB1A driven by abiotic stress inducible promoter rd29A in wheat seemed to delay development in the transgenic plants and did not result in better grain yields than the control under both irrigated and water-stress conditions. The growth retardation observed on the over-expression of AtDREB1A using 35S CaMV constitutive promoter was overcome using inducible promoter rd29A in transgenic Arabidopsis (Kasuga et al. 1999) and tobacco (Kasuga et al. 2004). However, in some of the transgenic wheat lines with rd29A:DREB1A, growth retardation was observed, which could be due to background expression of this promoter in wheat. We are now pursuing transgenic wheat plants with DREB1A under different inducible promoters, especially promoters with low background, which only switch on when plants are under certain specific

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stress conditions. For the evaluation of transgenic wheat plants, pot evaluation is important at early stage, but it is of great importance to assess transgenic material in the field as early as possible to investigate the impact on both plant growth and grain yield under various appropriate drought-stress profiles. It is also of interest to investigate at what stages of growth and in which genetic backgrounds the transcription factors like DREB1A may have their most significant effects. Heat stress already affects wheat plant senescence and photosynthesis, thereby influencing grain filling. Wheat cultivars capable of maintaining high 1000kernel weight under heat stress appear to possess higher tolerance to hot environments (Reynolds et al. 1994b). Physiological traits that are associated with wheat yield in heat-prone environments are canopy temperature depression, membrane thermo-stability, leaf chlorophyll content during grain filling, leaf conductance, and photosynthesis (Reynolds et al. 1998). Amani et al. (1996) used canopy temperature depression to select for yield under a hot, dry, irrigated wheat environment in Mexico, whereas Hede et al. (1999) found that leaf chlorophyll content was correlated with 1,000-kernel weight while screening Mexican wheat landraces. Such sources of alleles coupled with some of the above traits that defined a new wheat ideotype can provide means for genetically-enhanced wheat by design in heat-prone environments. As indicated above, there are two main wheat environments in the Indo-Ganges: mega-environment 1 is a favorable, irrigated, low rainfall environment with high yield potential. In contrast, mega-environment 5 is a heat-stressed environment (early and late season heat stress) with available irrigation, but in its humid and hot areas, the fungi Cochliobolus sativus cause spot blotch and the Pyrenophora tritici-repentis (Died.) Drechsler inducing tan spot are pathogens responsible for leaf blight (Joshi et al. 2007c). These two major wheat mega-environments in the subcontinent have been differentiated on the basis of coolest quarter minimum temperature ranges (3–11C for ME-1 and 11–16C for ME5). In some of the mega-environment five areas poorer infrastructure, socio-economic factors, and crop management coupled with the stresses, brought the shortened vegetative phase and leaf blight ensuing from heat stress, particularly after flowering stage, which leads

to low yield in wheat, the quality of which may be also affected by grain shriveling. Recent data compiled in the eastern Gangetic plains over 6 years have shown that the higher average temperature observed, especially during the night, was related to higher spot blotch severity and partly explained lower yield performances (Sharma et al. 2007). Disease severity which increases with growth stage depends on crop resilience to heat stress (Duveiller et al. 2005). Thus, improvement of spot blotch resistance in these areas implies a crop physiology adapted to stressed environments (Sharma et al. 2004). Such observations support, that under global warming, there will be a significant decrease of the most favorable and high yielding mega-environment 1 area due to heat stress, thereby leading to likely yield losses of the wheat grain harvest. Unless appropriate improved germplasm, crop husbandry, and resource management are deployed, about 200 million people (based on current population), whose food intake rely on crop harvests in mega-environment 1, will become more vulnerable due to this heat stress affecting the wheat-cropping systems. In this regard, better host plant resistance to leaf blight has been achieved by crossing genetic resistance sources or wild relatives to high-yielding cultivars (Duveiller 2004). Germplasm improvement methods centered on regional partnerships are now more specifically addressing the needs of warmer areas since it is possible to improve host plant resistance of local wheat cultivars based on selective breeding using resistant and agronomically-superior genotypes (Sharma et al. 2004).

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Mitigation to global warming

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Nitrous oxide (N2O) is a potent greenhouse gas generated through the use of manure or nitrogen (N) fertilizer and susceptible to de-nitrification, thus often unavailable for crop uptake and utilization. In many intensive wheat-cropping systems common N fertilizer practices lead to high fluxes of N2O and nitrous oxide (NO). Some plant species show biological nitrification inhibition (BNI) ability that would result in less flux of N2O and NO and retention of N fertilizer for longer time in the soil, which would lead to reducing greenhouse gas. However, wheat, rice, and maize—the most important cereal crops, do not possess BNI (Subbarao et al. 2007b). Leymus racemosus (Lam.) Tzvelev—a wild relative of wheat,

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was found to be a source for inhibiting or reducing soil nitrification by releasing inhibitory compounds from roots and suppressing Nitrosomonas bacteria (Subbarao et al. 2007a). A Leymus chromosome containing the relevant gene(s) was introduced into a wheat line that thereafter showed BNI. New research undertakings are underway to characterize and quantify the biological nitrification inhibition (BNI) ability from this Leymus-wheat introgression lines in field trials that may open the path for genetically enhancing BNI ability in the cultigen pool using this wild relative as a source for this trait.

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Food safety and fighting wheat mycotoxins

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Fusarium head blight (FHB) or scab is an important fungal disease that affects wheat by reducing kernel weight, yield, and flour-extraction rates in many important wheat-growing areas in North and South America, China, and Europe. Several Fusarium species are associated with scab: Fusarium graminearum Schwabe is the major pathogen worldwide while F. culmorum (Wm.G. Sm.) Sacc. tends to predominate in maritime regions (Gilchrist and Dubin 2002). The Fusarium species associated with scab produce mycotoxins that contaminate the grain. A number of these compounds have been shown to be harmful to human and animal health. The mycotoxins of primary concern with respect to FHB are the trichothecenes. The most common trichothecene in grain affected by scab is the mycotoxin known as deoxynivalenol (DON) produced by F. graminearum and F. culmorum (Nicholson et al. 2007). A second trichothecene produced by certain isolates of these two Fusarium species is nivalenol (NIV). Another mycotoxin, produced mainly by F. culmorum, F. graminearum, and F. cerealis (Cooke) Saccardo is zearalenone (ZEN), a metabolite that is less acutely toxic and often occurs with trichothecenes (Desjardins 2006; Nicholson et al. 2007). On wheat seedling tests, the addition of trichothecenes (DON, NIV, and T-2) to spore suspensions increases lesion size dramatically, unlike ZEN or mycotoxins produced by Fusarium species inducing disease on other cereals. This suggests that trichothecenes play an important role in lesion development by Fusarium species associated with FHB (Jiro Murakami, CIMMYT, unpublished). In recent years, the implementation of new and more stringent regulations

limiting the authorized level of DON in grain and food products has prompted wheat researchers and growers to give more attention to the need to produce wheat with lower amounts of mycotoxins (Ortiz et al. 2008a). Research toward improved resistance against FHB has been conducted at CIMMYT for more than 20 years and collaboration with institutes in China, Japan, and Brazil led to the incorporation of superior levels of scab resistance into high-yielding genotypes (Dubin et al. 1996; Ban et al. 2006). However, since the resistance is limited, research is ongoing to expand this resistance base through the identification and validation of QTL associated with field resistance and low levels of DON. In practice, germplasm screening, phenotyping of mapping populations, and detection of novel sources of resistance is conducted under strictly standardized field conditions at El Batań, where CIMMYT is located near Mexico City, under artificial inoculation of F. graminearum isolates for which the DON chemotype has been confirmed by the polymerase chain reaction (PCR). At harvest, due to the high cost of mycotoxin detection, only specific research materials and samples of elite wheat germplasm consistently showing a low visual Fusarium head blight index are ground to determine the DON level in the whole grain flour. Analysis for DON content is carried out by means of a commercially available immunoassay test (Ridascreen Fast DON, Biopharm, Germany). CIMMYT is also involved in research aiming at reducing mycotoxin testing costs in particular if a method is used by national research programs. Thus, for selected studies in collaboration with partners in South America, CIMMYT assesses and validates low-cost protocols to determine DON content based on fluorometry (Fuoroquant, Rohmer, Austria). Further applied research includes the validation of quantitative PCR methods aimed at quantifying DON based on the fungal biomass in the grain and the presence of the Tri-5 gene responsible for DON production, analyzing the correlation with FHB field symptoms. Other attempts to speed the detection of low DON content in advanced wheat lines included the evaluation of a lateral-flow colloidal gold-based immunoassay for the rapid detection of deoxynivalenol with two indicator ranges (De Saeger et al. 2008). One of the objectives of CIMMYT’s wheat breeding program in coming years is to distribute

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high-yielding wheat germplasm with acceptable enduse quality and with resistance to FHB which also harbor a low DON content. Thus, efforts are being made to add the information on the DON content in each line when nurseries are distributed (Lewis et al. 2007). Since the main obstacles to provide reliable quantitative information on resistance to mycotoxins (i.e., DON) in wheat germplasm are the high field evaluation and assay costs, understanding the factors affecting the correlation between phenotypical data and mycotoxin content is paramount to improve data accuracy and information reliability.

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Grain quality for adding value in the commodity chain

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Globalization, the continuous increase in urbanization, and improvements in the income of people in developing countries have been generating a large demand for wheat crops possessing specific quality traits. For example, consumption of western style food such as pan bread and cookies are increasing rapidly in large wheat-producing countries such as China and India, and consumption of flat breads and flour noodles are becoming popular as convenience foods in the western hemisphere. In addition, the demand for high quality traditional products such as noodles, steamed bread, flat breads, pasta or couscous among others, is also increasing quickly. Hence, grain-processing quality and quality uniformity are becoming more important breeding issues in developing countries. In wheat breeding, improving wheat productivity, disease resistance, and tolerance to biotic stresses and wheat quality attributes need to be addressed holistically to develop wheat cultivars satisfying both the producer and the consumer and in order to maintain competitive and sustainable production systems.

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End-use quality traits

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Flour yellowness is undesirable for producing breads and most Asian flour noodles (Liu et al. 2003), except for yellow alkaline flour noodles. In contrast, in durum wheat semolina, a high concentration of yellow carotenoids (mainly lutein) is highly desirable, for it results in bright, yellow pasta products. Sprouted grain shows high alpha-amylase activity, which negatively affects the processing quality of

bread-, cake- and cookie-making. Sound wheat may present different levels of poly-phenol oxidase activity, which promote the time-dependent darkening of cooked Asian noodles (Anderson and Morris 2003), and of lipoxygenase, which promotes the oxidation of carotenoids reducing pasta yellowness (Leenhardt et al. 2006). Hard wheat produces flours with much higher levels of starch damage and water absorption as compared to soft wheat. This difference in water-absorption capacity makes soft wheat (and not hard wheat) suitable for cookie making and hard wheat (and not soft wheat) suitable for bread making (Souza et al. 2002). Grain hardness is influenced mainly by allelic variations and is closely linked to puroindoline genes. Cane et al. (2004) observed that some allelic variations of Pina show differential effects on milling yield. The main factor determining wheat end-use is the gluten protein. Gluten is composed of monomeric gliadins and polymeric glutenins. Allelic variations controlling gliadin and glutenin composition (mainly at the Glu-1, Glu-3, and Gli-1 loci), are responsible for most variation in dough properties (strength and extensibility), dough-mixing properties, and breadand Chinese noodle-making quality (Branlard et al. 2001; He et al. 2005; Liu et al. 2005). In durum wheat, the best pasta-cooking quality is achieved from wheat possessing Glu-B3 LMW-2 type alleles (Penã and Pfeiffer 2005 and references therein). Granule-bound starch synthase (GBSSI) is responsible for amylose synthesis in the grain. Grain amylose levels are affected by allelic variations of the Wx gene complex (Geera et al. 2006). Starch pasting viscosity affects the eating quality of wheat flour noodles, particularly Japanese white noodles, which are smooth, soft, and slightly elastic (Crosbie 1991). Increased starch-swelling power and desirable noodle softness have been associated with the absence of GBSSI controlled by the Wx-B1a gene on chromosome 4A (Ross et al. 1996).

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Quality testing methodology

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CIMMYT addresses wheat quality improvement by examining and defining several factors associated with wheat processing and end-use quality, and by applying diverse molecular and conventional analytical and screening tools required to achieve the improvement of relevant grain quality-related traits.

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Ongoing research in China and Mexico are examples of this approach. Knowledge about the genetic control and the influence of allelic variants of main traits (Table 10) is fundamental for efficient quality improvement. However, we cannot ignore that some of these quality traits may be strongly influenced by genotype-byenvironment (heat, drought, high humidity) interactions (Eagles et al. 2002; Spiertz et al. 2006) and nutrient availability, particularly at the grain-filling stage (Dupont et al. 2006). At CIMMYT electrophoresis (SDS-PAGE) is commonly used to identify allelic variations at Glu1, Glu-3, and Gli-1 in parental lines. In addition, rapid, small-scale tests including marker-assisted selection (MAS), near-infrared spectroscopy (NIRS), SDS-sedimentation, and dough rheology, are applied at different stages of the breeding process. MAS offers the best option for specific traits controlled by single genes because it is performed on leaf tissue before seed-setting. The flour sedimentation test, NIRS, and the mixograph, on the other hand, allow rapid estimation of important physical, compositional, and functional grain and flour factors closely associated with milling and wheat processing quality. Finally, the use of flour and dough-testing methodologies (milling yield, dough viscoelasticity, starch pasting properties, and actual end-product quality) allow characterizing more specifically for processing and end-use quality attributes of advanced lines of spring and winter/facultative germplasm.

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Breeding strategy, quality testing, and screening

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In setting breeding priorities and strategies, one must determine: the cultivar’s intended end-uses and the

demands of the targeted market, specific quality traits to breed for, and genotype-by-environment-by-management interactions that may influence the quality of the resulting cultivar. Information on glutenin and gliadin subunit composition helps in the designing of crosses aimed at achieving allelic combinations known to contribute positively to dough properties required for producing leavened and flat breads, flour noodles, cookies, and pasta. Screening may initiate in F4–F5 applying MAS for desirable quality-related genes or allelic variations. When possible, the use of rapid, highthroughput conventional small-scale tests (e.g. SDSsedimentation and NIRS) should be used in addition to MAS to screen for complex traits under multigenic control. Because MAS and conventional small-scale quality tests explain end-use quality only partially (Graybosch et al. 1999; Kuchel et al. 2006), it is advisable to apply quality screening based on more specific processing traits (dough viscoelasticity and mixing properties, starch pasting properties, baking performance) and end-product quality attributes in advanced breeding stages; i.e., F6–F9 (Penã et al. 2002; Souza et al. 2002). Finally, multi-location yield trials exposing advanced elite lines to environmental variation (and farmers’ crop management practices) are necessary to identify the few genotypes combining stable yield and quality attributes across locations. China and CIMMYT have had a very strong and close collaboration regarding germplasm exchange, human resource development, and in the establishment of diverse analytical tests efficient to improve bread and noodle quality attributes. ‘Jinan 17’ and ‘Jimai 19’ are former leading cultivars in northern China, and ‘Jinmai 20’ and ‘Yumai 34’ are good panbread making quality and leading cultivars in the

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Table 10 Main wheat quality traits and their genetic control

Quality trait

Loci

Chromosome

Grain hardness (puroindolins)

PinA-D1, PinB-D1

5DS

Alpha amylase

Amy-1, Amy-2

Groups 6 and 7

Poly phenol oxidase

Ppo-A1, Ppo-D1

2AL, 2D

Protein content

Pro-1, Pro-2

5D

Glutenins

Glu-1, Glu-3

1A, 1B, 1D

Gliadins

Gli-1, Gli-2

Groups 1 and 6

Secalins

Sec-1

1R

Starch granule-bound synthase

Wx-A1, Wx-B1, Wx-D1

7AS, 4AL, 7DS

Yellow Pigment

PsyA1, Psy-B1

7A, 7B



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Yellow and Huai Valleys. They derived from CIMMYT-bred germplasm. Improvement of gluten quality is the top priority for quality breeding in China. SDS sedimentation value, mixograph parameters, and high- and low- molecular weight glutenin subunits are primarily used for characterization of crossing parents and selection in early generations. Selection of desirable grain hardness Pin-B1 alleles (Pinb-D1b) is highly desirable. Grain hardness, SDS sedimentation, peak viscosity, polyphenol oxidase (PPO) activity and yellow pigment content, can be used to screen for Chinese white noodle quality in the early generation of a wheat breeding program; molecular markers for selection of PPO activity (He et al. 2007), yellow pigment content (He et al. 2008), and high starch viscosity (Briney et al. 1998) are also available for screening. Molecular markers have been routinely used to characterize crossing parents and for confirmation of the presence of targeted genes in breeding programs, both in Mexico and China. Two multiplex PCR assays targeting improvement of bread-making quality (including five genes) and of noodle quality (including three genes) were also developed to improve the efficiency and reduce the costs of applying MAS in wheat breeding programs (Zhang et al. 2008).

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Future challenges in quality improvement

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The future challenge is to improve dough extensibility and quality stability. The combination of high yield potential and good quality and integration of diverse quality donors from wheat relatives is advisable. Wheat breeders still face the challenge of unveiling the complex mechanisms involved in genotype-byenvironment-by-management interactions affected by heat, drought, erratic climate, nutrient availability during grain development, among other factors that significantly influence yield and quality stability (Dupont et al. 2006; Eagles et al. 2002; Geera et al. 2006; Spiertz et al. 2006). Furthermore, an excess of three billion people in the world are affected by micronutrient deficiencies that cause serious health problems. In addition, obesity and associated illnesses are becoming serious public health problems in many parts of world. Breeders need to immediately start serious undertakings to improve wheat nutritional value and health-related issues associated with the consumption of wheat-based foods.

Human nutrition/health and wheat biofortification

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Zinc deficiency is implicated in health problems throughout the world, especially across a wide band of countries in West Asia, North Africa, and the South Asian subcontinent where more than half of inhabitants’ daily calories come from wheat (CIMMYT 2004). In South and West Asia, millions of heavy wheat consumers are also iron deficient. Women and children are particularly prone to zinc and iron malnutrition. The health of poor people may be enhanced by breeding staple food crops that are rich in micronutrients, a process referred to as biofortification. In 2003, the CGIAR launched the Challenge Program HarvestPlus with the aim of breeding and disseminating crops for better nutrition. Within this global alliance undertaking, CIMMYT is developing highyielding wheat cultivars with grain containing 30–50% more iron and zinc (Ortiz-Monasterio et al. 2007). The potential impact is dramatic given that wheat cultivars bred by CIMMYT and its partners cover 80% of the global spring wheat area. The best sources of these micronutrients are wild species that do not cross easily with modern wheats (Cakmak et al. 2000). Researchers have therefore developed a ‘‘bridge’’ line by crossing one such grass (Ae. tauschii) with a high-micronutrient primitive wheat (Triticum dicoccon Schrank). The resulting ‘‘bridge’’ lines combine readily with modern wheat cultivars, producing lines whose grain contains more iron and zinc than modern wheat. Partners in India and Pakistan are using this approach to develop highyielding, disease-resistant, biofortified wheat for South Asia. In Turkey, home to pioneering research on zinc deficiency and wheat, wheat landraces and cultivars that take up and use zinc more efficiently are being combined with wheat cultivars that have resistance to yellow rust and root diseases (CIMMYT 2004). CIMMYT researchers, with partners from labs elsewhere, are identifying molecular markers for genes that control grain iron and zinc levels, to facilitate their transfer to new cultivars. Recent research undertaken by CIMMYT on iron and zinc losses in milling and cooking, suggests that milling reduces Fe and Zn levels in the flour but hydrate is reduced even more which results in a more favorable Zn/hydrate ratio, which is highly correlated

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with bioavailability (Ortiz-Monasterio unpublished results). A flour extraction rate of 80% is best to optimize function of increasing bioavailability versus decreasing content with decreasing flour extraction. This and the center’s research on bio-availability will help determine exactly how much it helps to eat biofortified daily bread.

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Empowering rural people through participatory wheat improvement and seed systems

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Three-quarters of the world’s poorest people live below US$ 1 a day of which 37% are in South Asia. In this region, particularly in the eastern IndoGangetic Plains, there is a high level of poverty, malnutrition, and food insecurity. The number of poor people is expected to increase still further as population growth exceeds that of agriculture productivity. Wheat, covering an area of some 37 million ha, is one of the economic mainstays in the region. However, the productivity of wheat cropping systems lags far behind its potential. Hunger is inextricably linked to poverty and vulnerability. The millennium development goal of the elimination of extreme poverty and hunger can only be met by increases in agricultural productivity, particularly by resource-poor farmers, which is fundamental to growth and poverty reduction in the region. South Asia produced 101.3 million t of wheat in 2007. India and Pakistan harvested 74.9 and 23.3 million t, respectively. In spite of this output, the region is projected to have a wheat deficit of 21 million t by 2020 (Agcaoili-Sombilla and Rosegrant 1994). If these projections are correct, Pakistan will have the highest deficit with 15 million t, followed by Bangladesh with 4 million t. India would have to increase its production from the current 74.9 million t to about 90 (Joshi et al. 2007b) or 109 million t by year 2020 (Nagarajan 2005). To achieve this output, the average national wheat yield would have to increase from its current 2.63 t ha-1 to almost 4 t ha-1 in the next 12 years. This is a significant challenge given that resources for research in these countries are shrinking and that the present estimated yield gap between farmers and experimental yields is about 1.8 t ha-1 (Ortiz-Ferrara et al. 2007a). Surveys conducted in the region suggest that one of the main causes of low yields is the predominance of older (at least 1.5 decades) wheat cultivars. These

cultivars are genetically inferior to more recently bred-germplasm, and are increasingly susceptible to diseases. Seed replacement is around 10% and there is significant lack of access to seed of appropriate cultivars, especially for those that are adapted to marginal environments. The varietal adoption trends described above are in large part due to the poor extension and weak seed production systems prevalent in most of these countries. Hence, a system for dissemination of new technologies and for developing community seed industry by local farmers and their groups is important to empower rural people. It is essential to promote new materials and to also make crop production more profitable for farmers. CIMMYT, in partnership with the Center for Arid Zone Studies-Natural Resources (CAZS-NR, Bagor, Wales), has been collaborating with farmers, national programs, and other South Asian partners to promote improved wheat cultivars and new resource-conserving technology (RCT) options in farmers’ fields. Participation fostered among farmers, scientists, extension specialists, non-governmental organizations (NGOs), and the private sector includes participatory variety selection (PVS), and participatory evaluation of agronomic practices. Through PVS, several farmer-preferred technologies have been identified including wheat cultivars for adverse conditions in eastern Uttar Pradesh, India (Singh et al. 2007), and for boron deficiency in some locations of Nepal. There has been considerable improvement in farmers’s access to new cultivars and technologies in the rural areas. Yield increases (15–70%) have been achieved by resource-poor farmers through the adoption of new cultivars and RCT. The farmers have also made substantial cost savings and achieved higher yields through resource-conserving agronomic techniques such as zero- or reduced-tillage. Seed of the new farmer-selected cultivars has been multiplied by groups of collaborating farmers and widely distributed. Following this participatory research, several thousands of farming households have rapidly adopted cultivars and benefited from them. Seed saving by farmers and farmer-to-farmer seed spread of new cultivars has been evident which has brought sustainable impact. Strengthening and capacity-building of local institutions including community-based seed production and distribution has also been taking place. Both men and women farmers have been

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participating in this partnership in various activities addressing gender perspective and empowerment issues. They are willing to collaborate with all of the partners to improve the returns to wheat cropping systems through participatory approaches.

farmers have clean seed of their preferred cultivars for further planting. Often the participating farmers harvest more seed than they need. The additional seed is sold to other farmers in the community. Thus the new cultivars are spread from farmer to farmer.

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Partnerships for development, dissemination, and adoption of improved technologies for improving wheat productivity

Experiences in improving food security and income generation

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Participatory research and development has been reported as an efficient approach for up-scaling new agricultural technologies (Ortiz Ferrara et al. 2001; Witcombe et al. 2001). It is capable of better addressing farmers’ problems that very often are not recognized due to the complexity of farmers’ different situations and the vast diversity in farmers’ fields. Participatory research has been used to complement ongoing research to help farmers by providing them with a wider choice of options to evaluate under their own conditions (Witcombe et al. 1996, 2005). The ‘‘mother-baby’’ trial system, which was successfully used for maize in sub-Saharan Africa (Snapp 1999; de Groote et al. 2002), proved to be an efficient approach for developing and disseminating new cultivars and RCT options through close collaboration with farmers. Under this approach, a large number of ‘‘mother-baby’’ trials are grown in different villages to provide better options for farmers. The ‘‘mother’’ trial consists of 12–15 elite wheat lines or recently released cultivars, which include as check the most popular cultivars grown by farmers at each site. A number of ‘‘baby’’ trials, consisting of just one of the elite cultivars in the ‘‘mother’’ trial plus a local check, are grown around the ‘‘mother’’ trial in the same year. Also, seed multiplication plots of all the genotypes in the ‘‘mother’’ and ‘‘baby’’ trials are planted simultaneously to harvest clean seeds. Bred-lines and cultivars in the ‘‘mother’’ and ‘‘baby’’ trials are assessed in a collaborative and consultative mode by farmers. Quantitative feedback is analyzed and used to ascertain farmers’ preferences. Clean seed of the farmer-selected cultivars is distributed to collaborating farmers. In the following year, farmers’ selected genotypes are tested in large fields along with the farmers’ local cultivar. Farmers are trained on seed production to harvest quality seed from the large plots in the second year. In this way,

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In Nepal, a total of 26 wheat cultivars were tested in 63 villages in seven districts from 2002 to 2005. These cultivars were tested in a wide range of environments using two different sets of PVS ‘‘mother’’ trials. As a result, about seven bred-lines or cultivars were identified by participating farmers. Three released cultivars are under extensive seed multiplication by the public seed industry. Farmers in the southern lowlands and in the mid-central hills of the Kathmandu Valley are also involved in community seed production. These adoption trends have helped farmers in those areas to increase food sufficiency (i.e., households with sufficient food for the year) from 65% in 2002 to 71% in 2005. Also, there were households with food sufficiency for longer period in 2005 compared to 2002. These gains in food sufficiency are primarily attributed to three factors. The farmers reported that of the gains in food sufficiency, 41.3% was due to the cultivar, 44.4% from crop management including fertilizers, and 14.3% from irrigation. Farmers in Bangladesh have identified at least three new wheat cultivars since 2005. Farmers who have adopted them have increased their income (Table 11). The yield increase over the widely popular cultivar ‘Kanchan’ was 705 kg, which translates into additional income of about US$ 164 ha-1. Varietal diversification and income generation has also increased in eastern India as a result of collaboration with the Indian Council of Agricultural Research (ICAR) and the Rice-Wheat Consortium for the Indo-Gangetic Plains (RWC). Many farmers in Uttar Pradesh are successfully engaged in community seed production. At one of the sites, around one-third of the area came under seed production after 3 years of PVS. In general, farmers at the PVS sites recorded greater profits than at non-PVS sites. Around 83% of the farmers at the PVS sites responded that they were making a profit of at least US$ 67 ha-1. The profit increase was mainly due to increases in productivity, decreases in the cost

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Genet Resour Crop Evol Table 11 Income change in villages at Daulatpur, Hatiari and Jogda (Dinajpur, Bangladesh) due to farmer-preferred wheat cultivars and adoption of recommended practices after participatory varietal selection (2002–2005) Area (ha)

Farmer-preferred cultivars Total a

Additional income 91,000 Tk/ha Tk

67.71 2,274 40.96 2,979 108.67 2,540

705 266

Tk = Taka local currency, i.e., US$ 1 = Tk 58

80

1,704 4,521

361.0 361.3

27.26 72.34

388.26 9,479 433.64 3,990

resistance gene Sr31, which was initially transferred from rye to wheat, was identified. Race Ug99 was subsequently detected in Kenya and Ethiopia in 2005, in Sudan and Yemen in 2006, and in Iran in 2007. It is predicted that Ug99 will continue to migrate to North Africa, the Middle East, South Asia, and beyond through winds or other means. The most striking feature of Ug99 is that it not only carries virulence to gene Sr31 but also this unique virulence is present together with virulence to most of the genes of wheat origin, and virulence to gene Sr38 introduced into wheat from Aegilops ventricosa Tausch. and bred in several European and Australian cultivars and a small portion of new CIMMYT germplasm (Singh et al. 2006). This virulence combination might have accounted for the wide-spread Ug99 susceptibility in wheat cultivars worldwide. New variants of this race with virulence to Sr24 and Sr36 were detected in Kenya in 2006 and 2007, respectively. It is anticipated that mutation toward more complex virulence will likely occur as the fungal population size increases and selection pressure is placed on the population by cultivars protected by additional racespecific resistance genes. It is estimated that between 90 and 95% of the global wheat area is planted with wheat cultivars that are susceptible to Ug99 or its new variants.

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Ug 99 stem rust as a global emerging threat to wheat (food) supply

The Borlaug global rust initiative

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Stem or black rust of wheat is historically known to cause severe devastation; however, it remained under control for almost 40 years through the use of host plant resistance. In 1998, severe stem rust infections were observed on wheat in Uganda, and a race, commonly known as Ug99 (TTKSK on North American nomenclature system) with virulence on

Reducing the area planted to susceptible cultivars in primary risk areas of East Africa, the Arabian Peninsula, North Africa, the Middle East, and West/ South Asia is the best strategy if major losses are to be avoided. The ‘‘Borlaug Global Rust Initiative’’ (www.globalrust.org), launched in 2005, is using the following strategies to reduce the possibilities of

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of cultivation, and improved earnings due to quality seed production of farmer-preferred cultivars. Based on this new outcome, participatory seed production was carried out at all the locations where PVS activities were conducted with the objective of equipping and training farmers for seed production of high-yielding cultivars. As a result, they could multiply seed of their preferred cultivars and not be dependent on outside sources. This approach was expected to enhance farmers’ profitability through lowered seed costs, lower costs of production due to the adoption of RCT, and surplus grain from higher production. This concept could be extended to other crops. The participatory seed production was found extremely useful for participating farmers, since at almost all the locations they were able to learn to produce their own high quality seed. The impact of participatory seed production is being realized for the first time on such a wide scale in the area and several farmers’ societies for seed production have been established in eastern Uttar Pradesh and the bordering districts of Bihar. This farmer-participatory approach has helped resource-poor farmers improve their livelihoods, while ensuring staple food for the region through the adoption of new cultivars and other RCT options.

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Old popular cultivar ‘Kanchan’

Seed Seed Price of Yield Yield saved in (kg ha-1) increase saved (kg ha-1) (kg ha-1) 52% area Saved Seed Add prod (kg) (91,000 Tk)a (91,000 Tk)

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major epidemics: monitoring the spread of race Ug99 beyond eastern Africa for early warning and potential chemical interventions, screening of released varieties and germplasm for resistance, distributing sources of resistance worldwide for either direct use as varieties or for breeding, and breeding to incorporate diverse resistance genes and adult plant resistance into high-yielding adapted cultivars and new germplasm. An aggressive strategy to identify and promote high-yielding, resistant cultivars is the only viable option to reduce potential losses as resource-poor and commercial farmers in most of Africa, the Middle East, and Asia cannot afford chemical control or may not be able to apply chemicals in the event of large scale epidemics due to their unavailability for timely application. Reduction of susceptible cultivars throughout the primary risk area should reduce wind dispersal of spores from these areas to the secondary risk areas.

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Strategy to breed race-specific resistance genes

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The high frequency of the highly resistant wheat materials from South America, Australia, the USA, and CIMMYT was identified through the 2005 and 2006 screenings with Ug99 in Kenya. They possess Sr24, located on the Th. elongatum translocation on chromosome 3DL together with the leaf rust resistance gene Lr24. The presence of race TTKST with Sr24 virulence at low frequencies in Ug99 lineage during 2006 resulted in a rapid buildup sufficient to cause an epidemic on the Sr24-carrying cultivar ‘Kenya Mwamba’ in 2007, which occupied about 30% of the Kenyan wheat area. The situations described above have once again reminded us of the consequence of dependence on single racespecific genes in the control of stem rust in areas where rust is endemic. Diverse sources of effective race-specific resistance genes, mostly derived from wheat relatives, are available for breeding. Genes Sr25 and Sr26, derived from Th. elongatum, have been previously used successfully in developing cultivars. Other genes, practically not used in wheat improvement but that may have good chances of succeeding are Sr27 of rye origin, and Sr22 and Sr35 derived from T. monococcum. Although alien resistance genes Sr29, Sr32, Sr33, Sr37, Sr39, Sr40, and Sr44 have not been used widely in breeding, preliminary experience has

indicated their association with unwanted agronomic traits and therefore sizes of alien chromosome segments must be reduced before they can be used successfully. The undesignated resistance genes SrTmp (wheat origin), SrR and Sr1A.1R (rye origin), and a few other uncharacterized sources originating from re-synthesized hexaploid lines or bread wheat offer further diversity. The fastest way to reduce the susceptibility of important wheat cultivars and the best new germplasm is to systematically incorporate diverse sources of resistance through limited or repeated backcrossing. Because most of these Ug99-effective genes are of alien origin, co-segregating molecular markers for some of them are already available and being used for selection at CIMMYT. To avoid fast breakdown, the best strategy is to use race-specific resistance genes in combinations. Molecular markers provide a powerful tool to identify plants that carry combinations of resistance genes. Markers for other genes need to be developed to facilitate their utilization. One major issue remains in that various currentlyeffective resistance genes are already present in some advanced spring breeding materials that are being tested in various countries to mitigate the immediate threat from Ug99. Whether of not they should they be deployed until their combinations are developed, is a difficult issue to resolve, and there is a wide range of opinions on the matter. This has provoked the CIMMYT wheat improvement group to focus their breeding efforts towards breeding minor genes based on adult plant resistance, especially for areas considered to be under high risk and where survival of the pathogen for several years is expected due to the presence of susceptible hosts and favorable environmental conditions. It is thought that this strategy will allow other areas of the world, especially facultative and winter wheat growing regions to use race-specific resistance genes more successfully in their breeding programs.

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Identification and breeding for complex adult plant resistance

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Durable stem rust resistance of some of the older US, Australian, and CIMMYT spring wheat lines and cultivars is believed to be due to the deployment of Sr2 in conjunction with other unknown minor, additive genes that could have originated from

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‘Thatcher’ and the ‘Thatcher’-derived line ‘Chris’ (Singh et al. 2006). Sr2 can be detected through its complete linkage with pseudo-black chaff phenotype. Genotypes with negligible expression of pseudoblack chaff can be selected in breeding materials. Sr2 does not confer adequate resistance under high disease pressure when present alone. It was detected in several highly-resistant old, tall Kenyan cultivars, including ‘Kenya Plume’ and the CIMMYT-derived semi-dwarf wheat lines ‘Pavon 76,’ ‘Kritati,’ and ‘Kingbird.’ ‘Pavon 76’ and ‘Kiritati’ were resistant since the initiation of rigorous screening in 2005 at Njoro (Kenya) with maximum disease scores of 20MR-MS. ‘Kingbird,’ a new advanced line, is at present the best known source of adult plant resistance in semi-dwarf wheat with maximum score recorded to be 5 MR-MS during the same period. Because these wheat lines are susceptible as seedlings with Ug99, their resistance is speculated to be based on multiple additive genes where Sr2 is an important component. With the exception of Sr2, little is known on the genes involved in durable adult plant resistance. However, earlier work done by Knott (1982), knowledge on durable resistance to leaf and yellow rusts (Singh et al. 2004), and observations made on breeding materials and a F6 mapping population involving ‘Pavon 76,’ indicate that the rate of rust progress is a function of the cumulative effect of the number of minor genes present in a genotype and the individual effects of each gene. Accumulation of four to five slow-rusting, minor genes is therefore expected to retard disease progress to rates that result in negligible disease levels at maturity under high disease pressure, described as ‘‘near-immunity’’ by Singh et al. (2000). Because a large portion of CIMMYT high-yielding spring wheat germplasm does not carry effective race-specific stem rust resistance genes to Ug99 and several lines were identified to carry at least moderate levels of resistance, we view this as a perfect opportunity to reconstitute high levels of adult plant resistance in new wheat materials. Due to the lack of molecular markers for adult plant resistance genes and the absence of the Ug99 race in Mexico, a shuttle breeding scheme between two Mexican sites and Njoro was initiated in 2006 to transfer or accumulate high levels of adult-plant resistance identified in semi-dwarf CIMMYT wheat lines to a range of

important wheat germplasm. We expect that the frequency of advanced lines which carry high yield potential and maintain wide adaptation, end-use quality characteristics, and high levels of resistance to all three rusts, will increase over time through the use of the Mexico-Kenya shuttle breeding.

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Replacing susceptible cultivars in Africa, the Middle East, and Asia

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Screening in Kenya during 2005, 2006, and 2007 has identified a few resistant released cultivars or advanced breeding materials at various stages of testing in most of the countries that submitted their materials for screening. One strategy is to find ways to ensure that the best, high-yielding resistant materials occupy at least 5% of total wheat area distributed throughout the wheat region and are readily available for use as seed in the case that Ug99 establishment is evident in a particular country. To occupy a large area the resistant cultivars must have superior yields to current popular cultivars. This objective is achievable as most of the current popular cultivars were bred during early- to mid-1990s, and the yield potential of current CIMMYT spring wheat germplasm has progressed significantly since then. Yield performances of 14 new high-yielding, Ug99resistant wheat lines together with current cultivars were determined during the 2006–2007 crop season at 27 sites in India, Pakistan, Nepal, Afghanistan, Iran, Egypt, Sudan, Syria and Mexico. Results show that at least three lines, possessing race-specific or adult plant resistance, in each country showed yield superiority in the range of 10–15% over the current local cultivars. These superior lines are being tested more extensively during the 2007–2008 season for their performance in the above countries and seed is being multiplied simultaneously. Testing of additional wheat materials, mostly with adult plant resistance, is also underway.

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Fitting bred-genotypes into sustainable and improved crop management practices

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Crop system management research adds value to improved germplasm by increasing the degree to which yield potential is achieved—about half of the increase in wheat productivity at the farm level is often attributed to crop system management and more

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crop breeding, ensued by improving crop management as occurred by 26 years of breeding. In addition, two other factors are apparent. Firstly, the linear slopes were different (36 kg ha-1 year-1 for normal trial management versus 52 kg ha-1 year-1 for the improved trial management) and the estimated annual rate of yield increase was different (0.52% year-1 for normal trial management versus 0.68% year-1 for the improved trial management. Secondly, one can observe the contrasting interacting yield performance of the cultivars developed between 1981 and 1987. For the normal trial management, yields went down for these cultivars whereas for the improved trial management they went up, which could indicate the need for improving phenotyping for yield potential and the appropriate crop management practices for station field testing.

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Wheat global partnership network builds national capacity through human resources development

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More than 40 years history of international wheat nursery trials, underpinning the voluntary collaboration of primarily public wheat improvement institutions, has been accompanied in parallel by intensive capacity-building efforts. More than 2000

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in stressed environments—and there is often synergy between these effects (the G 9 System interaction). CIMMYT holds a unique comparative advantage for such research at the interface between crop improvement and crop system management. Figure 5 shows the important role of crop management regarding maximizing yield potential. The lower line shows the yields of a historical set of wheat cultivars bred from 1962 to 1988 based on applying the current crop management practices that were used at that time by station management for the fully irrigated yield trials to determine the yield potential for new CIMMYT materials. The upper line presents the yields for the same set of lines but following improved crop management practices that incorporated the use of deep chiseling to break up existing soil compaction zones, combined with the use of the Sesbania spp. summer green manure crop and chicken manure to try to rapidly enhance the extremely low level of soil organic matter content. This trial shows therefore the benefits of deep chiseling (about 50–70 cm chisel depth, with shanks 50 cm apart) and of using organic matter (green and chicken manure). As can be seen in Fig. 5, almost as much progress in improving wheat yield potential—after 26 years of Fig. 5 Wheat grain yield using normal and agronomically improved yield trial management (Obregon, Mexico, 1987– 1988)

Comparison of the yield performance of a historical set of cultivars for the normal CIMMYT, irrigated yield trial management in Obregon in 1988 versus agronomically improved trial management

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Year of Cultivar Release Normal CIMMYT Yield Trial Management in 1988 Agronomically Improved Yield Trial Management Linear (Agronomically Improved Yield Trial Management) Linear (Normal CIMMYT Yield Trial Management in 1988)



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Country of origin

Group trainees

Visiting researchers

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Developed world

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scientists and research technicians from developing countries have participated in CIMMYT’s in long term hands-on courses organized in research stations in Mexico and a similar number of visiting scientists have come to CIMMYT to work shoulder to shoulder with CIMMYT scientists in the research and farmers fields, laboratories, and in the genebank (Table 12). Several hundreds of graduate students also had opportunity to conduct their thesis research with financial or technical support from CIMMYT. A number of short term special courses have been organized annually in collaborating countries particularly since the 1980s. Recently however, there has been increasing concern globally about who will prepare the crop breeders of the twenty first Century as the number of public breeders, who produce new cultivars, is steadily declining. This pattern is not limited to the developed world, but has been reported from many developing countries as well (Guimara˜es et al. 2006a, b, 2007). The genetic enhancement of wheat is not an exception, but maybe a more difficult case. Wheat breeding remains primarily in the domain of the public sector. Skilled wheat breeders in developing countries prepared in 1960s and 1970s are now either retiring or have been promoted to higher administrative positions in their institutions and are not actively in charge of active breeding programs. They are being replaced by scientists involved in more basic genetic studies, with less field experience. This shift is fueled by the perception that private-sector breeding efforts are adequate to meet cultivar needs. Also cuts in university resources have led to reduced support of field programs, and this has pushed the current public plant breeders to shift their activities toward fundamental or basic studies that can be supported by federal grants and the private sector. The loss of plant breeding programs is of great concern to both the USA plant breeding industry and the international community (Hancock 2006).

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Outlook: seeding innovations … nourishing hope

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These are some of the issues that research managers and wheat scientists must now confront in order to select an optimal portfolio of strategic wheat genetic enhancement research for the coming years, which will have an impact on the ground during the coming decades. Until the dramatic expansion of demand for maize biofuels and the weather-induced supply problems in the past few years, the prospects for a reversal of the steady fall of the real prices of cereals

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Region

Furthermore, an effective and close partnership with national researchers remains as one of the major challenges to the successful mission of international crop breeding. Their resources have been diminishing in terms of human and infrastructural capital to enable this to occur. However, some national partners have strengthened their research capacity significantly (e.g. Brazil, China, India, Mexico, South Africa) over the past 40 years and their needs for capacity building are less, and they work more in equal partnership with the international breeding programs. Hence, one of the overriding challenges for many national partners will be to include in their national institutional frameworks, investments in research-for-development to ensure that the level of science and resources are enough to provide basic support and allow key outputs to be achieved. It is clear that without sufficient national capacity the use of international public goods produced in partnership with international breeding programs, such as CIMMYT, will be restricted, and the mission therefore compromised. In order to develop the strategies to prevent further erosion of institutional plant breeding training capacity, several broadly attended meetings have been conducted recently. Based on its broad scale study of national capacities in plant breeding, the United Nations of the Food and Agriculture Organization (FAO) launched the Global Partnership Initiative for Plant Breeding Capacity Building in 2006. In accordance with its strategy and in order to address the above described tendency, CIMMYT will continuously support capacity-building of wheat scientists in NARS through manifold ways—basic and advanced courses on wheat improvement, visiting scientist stays, and the support of degree thesis research.

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Table 12 Number of benefitting countries, long-term group trainees and visiting researchers on wheat improvement at CIMMYT



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including wheat appeared poor. Recent projections suggest a long-term increase in the real price of wheat along with other cereals (von Braun 2007). There are a number of trends and predicted key factors on which to base decisions: for example, the growing world population needs more food, more energy, and more feed grain to supply an ever increasing global demand for animal products; decreasing water supplies for agriculture and the effects of climate change are increasing the levels of abiotic stress across major wheat-producing areas; the application of biotechnologies for better use of wheat genetic resources in the betterment of the crop is likely to offer new opportunities to increase yield, providing the private sector is also sufficiently engaged. As shown by this article, CIMMYT and research partners worldwide are conserving the wheat genetic endowment and improving crop yields and stability across the major cropping systems where wheat thrives. Likewise, this manuscript illustrates how such genetic resources are addressing new global challenges to both wheat production and demand, especially for the still growing population of the developing world. Surely, the wealth of genetic resources available in the wheat gene pools (including wild species) will be among the important sources available to plant breeders in their quest for high and stable yielding wheat cultivars that meet the end use quality demands at a time of limited resources and global warming.

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Acknowledgement The authors thank Ms. Allison Gillies (CIMMYT, Mexico) for editing an early version of this manuscript. We acknowledge the kind support of the CGIAR members for wheat improvement at CIMMYT through unrestricted funding and other resources brought by special project grants in recent years from Australia, Belgium, Bill & Melinda Gates Foundation, Canada, China, Denmark, European Commission, FAO, FONTAGRO, Generation Challenge Program, Germany, HarvestPlus, India, Iran, Italy, Japan, Mexico, Norway, Republic of Korea, Rockefeller Foundation, Sasakawa Africa Association, Spain, Sweden, Turkey, United Kingdom, United States of America and the World Bank, as well as the in-kind contributions of national partners elsewhere.

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References

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Amani J, Fischer RA, Reynolds MP (1996) Canopy temperature depression association with yield of irrigated spring wheat cultivars in a hot climate. J Agron Crop Sci 176: 119–129 Anderson JV, Morris CF (2003) Purification and analysis of wheat grain polyphenol oxidase (PPO) protein. Cereal Chem 80:135–143 Anderson JA, Stack RW, Liu S, Waldron BL, Fjeld AD, Coyne C, Moreno-Sevilla B, Mitchell FJ, Song QJ, Cregan PB, Frohberg RC (2001) DNA markers for Fusarium head blight resistance QTLs in two wheat populations. Theor Appl Genet 102:1164–1168 Austin RB, Bingham J, Blackwell RD, Evans LT, Ford MA, Morgan CL, Taylor M (1980) Genetic improvement in winter wheat yields since 1900 and associated physiological changes. J Agric Sci (Cambridge) 94:675–689 Ban T, Lewis JM, Phipps EE (eds) (2006) The global Fusarium initiative for international collaboration. CIMMYT, Mexico Barnabas B, Jager K, Feher A (2008) The effect of drought and heat stress on reproductive process in cereals. Plant Cell Environ 31:11–38 Bartlett PW (2000) New pests and diseases in European Community plant health legislation. In: The BCPC conference-pests and diseases, 2000 9B-4, pp 1159–1165 Bell MA, Fischer RA, Byerlee D, Sayre K (1995) Genetic and agronomic contributions to yield gains: a case study for wheat. Field Crops Res 44:55–65 Branlard G, Dardevet M, Saccomano R, Lagoutte F, Gourdon J (2001) Genetic diversity of wheat storage proteins and bread wheat quality. In: Bedo Z, Lang L (eds) Wheat in a global environment. Kluwer Academic Publishers, Dordrecht, pp 157–169 Brennan JP, Warham EJ, Byerlee D, Hernandez-Estrada J (1992) Evaluating the economic impact of quality-reducing, seed-borne diseases: lessons from Karnal bunt of wheat. Agric Econ 6:345–352 Briney A, Wilson R, Potter RH, Barclay I, Crosbie G, Appels R, Jones MG (1998) A PCR marker for selection of starch and potential noodle quality in wheat. Mol Breed 4:427– 433 Buerstmayr H, Lemmens M, Hartl L, Doldi L, Steiner B, Stierschneider M, Ruckenbauer P (2002) Molecular mapping of QTLs for Fusarium head blight resistance in spring wheat. I. Resistance to fungal spread (type II resistance). Theor Appl Genet 104:84–91 CABI (2005) Crop protection compendium, global module. CAB International, Wallingford Cakmak I, Ozkan H, Braun HJ, Welcj RM, Romheld V (2000) Zinc and iron concencetrations in seeds of wild, primitive and modern wheats. Food Nutr Bull 21:401–403 Cane K, Spackman M, Eagles HA (2004) Puroindoline genes and their effects on grain quality traits in southern Australian wheat cultivars. Aust J Agric Res 55:89–95 CGIAR (1999) CGIAR Center statements on genetic resources, intellectual property rights, and biotechnology. May 1999. Center Directors and Center of Board Chairs of CGIAR, Washington Chen S, Ravallion M (2007) Absolute poverty measures for the developing world, 1984–2004. Proc Natl Acad Sci (USA) 104:16757–16762

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Evenson RE, Gollin D (2003) Assessing the impact of the Green Revolution: 1960 to 2000. Science 300:758–761 FAO (1983) Commission on plant genetic resources. Resolution 8/83 of the 22nd Session of the FAO conference. Food and Agriculture Organization, Rome FAO (2002) The international treaty on plant genetic resources for food and agriculture. Food and Agriculture Organization, Rome FAO (2007) Commission on genetic resources for food and agriculture. Food and Agriculture Organization, Rome. http://www.fao.org/ag/cgrfa/itpgr.htm (January 2007) Fischer RA, Rees D, Sayre KD, Lu Z-M, Condon AG, Larque Saavedra A (1998) Wheat yield progress associated with higher stomatal conductance and photosynthetic rate, and cooler canopies. Crop Sci 38:1467–1475 Flint-Garcia SA, Thornsberry JM, Buckler ES (2003) Structure of linkage disequilibrium in plants. Annu Rev Plant Biol 54:357–374 Frankel OH (1977) Natural variation and its conservation. In: Muhammed A, von Botstel RC (eds) Genetic diversity of plants. Plenum Press, New York, pp 21–24 Geera BP, Nelson JE, Souza E, Huber KC (2006) Granule bound starch synthase I (GBSSI) gene effects related to soft wheat flour/starch characteristics and properties. Cereal Chem 83:544–550 Gilchrist L, Dubin HJ (2002) Fusarium head blight. In: Curtis BC, Rajaram S, Go´mez Macpherson H (eds) Bread wheat: improvement and production. Food and Agriculture Organization, Rome, Italy. Plant Prod Protect Ser 30:279– 283, 285–299 Gill B, Friebe S (2002) Cytogenetics, phylogeny and evolution of cultivated wheats. In: Curtis BC, Rajaram S, Go´mez Macpherson H (eds) Bread wheat improvement and production. Food and Agriculture Organization, Rome. Plant Prod Protect Ser 30:71–88 Global Crop Diversity Trust (2007) Global strategy for the ex situ conservation with enhanced access to wheat, rye and triticale genetic resources. Global Crop Diversity Trust, Rome, http://www.croptrust.org/main/strategies. php?itemid=37 Graybosch RA, Peterson CJ, Hareland GA, Shelton DR, Olewnik MC, He H, Stearns MM (1999) Relationships between small-scale wheat quality assays and commercial test bakes. Cereal Chem 76:428–433 Guimara˜es EP, Bedoshvili D, Morgounov A, Baboev S, Iskakov A, Muminjanov H, Kueneman E, Paganini M (2006a) Plant breeding and related biotechnology competence in Central Asia and recommendations to strengthen regional capacity. Agromeridian 2(3):137–143 Guimara˜es EP, Kueneman E, Carena MJ (2006b) Assessment of national plant breeding and biotechnology capacity in Africa and recommendations for future capacity building. HortScience 41:50–52 Guimara˜es E, Kueneman E, Paganini M (2007) Assessment of the national plant breeding and associated biotechnology capacity around the world. Crop Sci 47:S262– S273 Hammer K (1980) Zur Taxonomie und Nomenklatur der Gattung Aegilops. Feddes Repert 91:227–247 Hancock JF (2006) Introduction to the symposium: who will train plant breeders? HortScience 41:28–29

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