Orchid Improvement in Chinese Taipei

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Orchid Improvement in Chinese Taipei. S.W. Chin, T.C. Cheng and F.C. Chen. Department of Plant Industry. National Pingtung University of Science and ...
Orchid Improvement in Chinese Taipei S.W. Chin, T.C. Cheng and F.C. Chen Department of Plant Industry National Pingtung University of Science and Technology Chinese Taipei Keywords: plant variety protection, pollination, hybridization barrier, international market competitiveness, Variety Protection Act Abstract Several economically important orchid genera and some other minor ones have been explored in Chinese Taipei for moderate to large scale production. Among them, Doritaenopsis, Phalaenopsis, Cattleya, Oncidium alliance and Paphiopedilum are emphasized by the orchid industry for both domestic and foreign markets. Chinese Taipei exports large quantities of Phalaenopsis young and flowering plants to many countries, such as Japan, USA, and the EU. Notably Phalaenopsis pot plants grown with sphagnum moss in certified greenhouses can be exported to the USA upon obtaining permission, which makes the annual export values increase steadily. Nobile Dendrobium is also being considered as a potential new potted orchid crop for the international market due to the feasibility of flower induction by low temperature for scheduled production. To maintain international market competitiveness, new hybrids or cultivars protection is utmost important in the target markets. One can now apply for breeder’s right in Chinese Taipei as well as to The Netherlands, in addition to applying the plant protection in the USA. Chinese Taipei’s government has passed the Variety Protection Act since 1988 and many new orchid cultivars have been increasingly applied for protection every year. To select a new orchid hybrid, in vitro seed germination and micropropagation for clonal production of planting propagules for export are emphasized by the industry, in addition to the government supported academic research towards industry-based problem solving studies. In the meanwhile, hybridization barrier may prevent efficient development of novel hybrids. Pollen meiotic analysis and pollination will be used as clues to look for a better strategy to overcome hybridization barriers in Phalaenopsis and nobile Dendrobium orchids. INTRODUCTION Orchids have been selected as potential flower crops for research and development in Chinese Taipei. Among them, Phalaenopsis, Oncidium, Paphiopedilum and nobile Dendrobium orchids received more inputs in aspects of cultivation, physiology, genetics and breeding. The breeder’s right has been approved by Chinese Taipei’s government since 1988. Now, one can apply for plant variety protection of several economically important orchids once a novel hybrid is created by conventional cross hybridization. However, about 60% of pollination failed to set fruits in most orchid genera. It is thus important to resolve the problem of hybridization barriers which may help us finding clues to overcome the barriers and enhance breeding efficiency. MATERIALS AND METHODS Information on the applications for plant variety protection of orchid crops was retrieved from the Council of Agriculture (http://newplant.coa.gov.tw) and data grouped according to year and orchid genera. To evaluate fertility of nobile Dendrobium hybrids, pollen tube growth was observed under fluorescent microscope after fixing stigma and styles in acetic alcohol solution and staining in aniline blue solution (Singh, 2003). Pollination failure in selfing or crossing were recorded after 1 to 16 days and ranked into 3 groups. Fruit set status in self-pollination was evaluated after 4 months and grouped by their color patterns. Proc. IS on Orchids and Ornamental Plants Eds.: N. Chomchalow et al. Acta Hort. 1025, ISHS 2014

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Sporad type analysis of Doritaenopsis Sogo Vivien ‘F1884’ pollen mother cells (PMC) was performed according to Bolaños-Villegas and Chen (2007) and BolañosVillegas et al. (2008). For comparison of temperature effect on tetrad frequency, all visible flower buds and open flowers of potted plants of ‘F1884’ were removed and transferred into to a forcing room with day/night temperature of 20°C. Two weeks later, the plants were divided into two groups and incubated in two different day/night temperature regimes of 22/20 and 28/25°C for three weeks. Sporads were observed and counted under microscope when the flowers opened. RESULTS AND DISCUSSION Application for Breeders’ Right in Chinese Taipei As the Act was approved in 1988, applications for variety protection of Phalaneopsis and Doritaenopsis cultivars increased steadily since 2002 until now, with a total of 463 cases (Table 1). Applications for other orchid genera include Oncidium, Cattleya, Dendrobium, Pleione, Cymbidium, Ludochilus and Angulocaste. More orchid genera will be approved in the near future when the DUS test guidelines are ready. Pollination and Fruit Set in Nobile Dendrobium In self-pollinations, about 22 to 43% flowers aborted 1 to 16 days after pollination, while 29 to 38% failed in cross pollination. This result suggests certain unknown prezygotic barriers may manipulate in nobile Dendrobium hybrids (Table 2). Also for general overview of fruit set condition, hybrids of same color types were grouped together and each self-pollinated. The highest successful fruit set occurs in red hybrids and similar in other color types. In the contrary, fruit set aborted less in red colored hybrids as compared to other groups. As the ploidy level of nobile Dendrobium hybrids was not evaluated prior to pollination study, it would be interesting to check the efficiency in fruit and seed set by separating hybrids into tetraploid and diploid, and possibly other ploidy levels. In compatible pollination, pollen tubes could be observed to extend in the styles one week after (Fig. 1). Compatible and incompatible pollination could also be observed after 14 days, with entangled or distorted pollen tubes suggesting occurrence of incompatibility (Fig. 2). (Jaiki and Chin, 2007) The seed amount in a fruit and subsequent in vitro germination may indicate the degree of hybridization efficacy as shown in Figure 3. Sporad Frequency under Different Temperatures When the flowering plants of ‘F1884’ at meiotic stage were grown under lower day/night temperature (22/20°C), higher percentage of normal tetrads was observed. Under higher day/night temperature (28/25°C), less normal tetrads was obtained. As previously reported, we showed that PMC with higher tetrad ratio tends to have higher fertility (Bolaños-Villegas and Chen, 2007; Bolaños-Villegas et al., 2008). This suggests cool temperature treatment may be helpful to enhance breeding efficiency by increasing normal tetrad percentage. ACKNOWLEDGEMENTS The works reported here were supported by grants from the Council of Agriculture and Agriculture and Food Agency, Chinese Taipei. Literature Cited Bolaños-Villegas, P. and Chen, F.C. 2007. Cytological identification of chromosomal rearrangements in Doritaenopsis and Phalaenopsis. J. Int. Coop. (Taiwan) 2:1-11. Bolaños-Villegas, P., Chin, S.W. and Chen, F.C. 2008. Meiotic chromosome behavior and capsule setting in Doritaenopsis hybrids. J. Amer. Soc. Hort. Sci. 133:107-116. Hsu, S.C., Cheng, T.C., Bolaños-Villegas, P., Chin, S.W. and Chen, F.C. 2010. Pollen meiotic behavior in relation to Phalaenopsis breeding. Acta Hort. 878:139-144. 190

Jaiki, M. and Chin, S.W. 2007. Study of pollen-pistil relationship between eggplant (Solanum melongena L.) and its wild relative Solanum torvum SW. J. Int. Coop. (Taiwan) 2:90-106. Singh, R.J. 2003. Plant Cytogenetics. 2nd ed. CRC Press, Boca Raton, FL, USA. Tables Table 1. Application for orchid variety protection in Chinese Taipei since 2002. Genera 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2 1 5 7 8 14 1 Oncidium 8 11 11 11 8 9 26 16 18 26 Phalaenopsis 3 6 1 22 20 20 46 50 73 78 Doritaenopsis 1 1 1 Cattleya 2 Dendrobium 2 2 Pleione 1 Ludochilus 2 Cymbidium 1 Angulocaste

Table 2. Pollination failure after different time between selfing and crossing in nobile Dendrobium.

Self-pollination Cross-pollination

I* 43 (77/179) 33 (135/405)

Time to abortion (%) II 22 (40/179) 29 (118/405)

III 35 (62/179) 38 (152/405)

* I, failure after 1~9 days; II, failure after 9~16 days; III, failure after more than 16 days.

Table 3. Selfing and fruit set status in different color groups of nobile Dendrobium.

Successful Aborted

Red 58 (80/138) 42 (58/138)

Fruit set (%)* Picotte White 32.5 (51/157) 32.9 (27/82) 67.5 (106/157) 67.1 (55/82)

Yellow 30.3 (37/122) 69.7 (85/122)

* recorded number of fruit set or failure divided by total pollinated flowers after 4 months.

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Figures

Fig. 1. Pollen tube growth of Dendrobium Red Emperor ‘Prince’ seven days after selfpollination. Bars = 0.1 mm. (a) pollen germinated on stigma; (b) pollen tube growth into style; c) pollen tubes penetrated into ovary.

Fig. 2. Comparing incompatible (a, b) and compatible (c, d) pollen tube growth of nobile Dendrobium on the way to ovaries 14 days after pollination.

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Fig. 3. Seed amounts in capsules (upper tier) and their corresponding germination status (lower tier) of different hybridization of nobile Dendrobium. 100

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Fig. 4. Tetrad ratio and bud size relationship of Doritaenopsis Sogo Vivien ‘F1884’ under 22/20°C (top) and 28/25°C (bottom) during meiosis stage. 193

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