Distribution of Heterodera glycines Races in Illinois ... the occurrence and distribution of races in Illinois need clarification. Forty-four .... Clinton-27. 0.0. 0.0. 0.0.
S u p p l e m e n t to J o u r n a l o f N e m a t o l o g y 2 3 ( 4 S ) : 6 2 4 - 6 2 8 . 1991. © T h e Society o f N e m a t o l o g i s t s 1991.
Distribution of Heterodera glycines Races in Illinois E. J. SIKORA1 AND G. R. NOEL9 Abstract: B e c a u s e t h e race s c h e m e f o r Heterodera glycines was e x p a n d e d recently f r o m 5 to 16 races, t h e o c c u r r e n c e a n d d i s t r i b u t i o n o f races in Illinois n e e d clarification. F o r t y - f o u r p o p u l a t i o n s o f H. glycines were collected f r o m sites in 23 o f t h e 88 i n f e s t e d counties. P o p u l a t i o n s were tested u s i n g t h e differential s o y b e a n lines Pickett 71, P e k i n g , PI 8 8 7 8 8 , a n d PI 9 0 7 6 3 . L e e 68 a n d Williams 82 were u s e d as s t a n d a r d s . Seedlings were g r o w n in 7 . 5 - c m - d clay p o t s a n d i n o c u l a t e d with 1,000 eggs a n d s e c o n d - s t a g e j u v e n i l e s o b t a i n e d f r o m H. glycines-infested field soil. Plants were m a i n t a i n e d in a g r e e n h o u s e at 2 2 - 2 8 C. A f t e r 1 m o n t h , t h e n u m b e r o f f i r s t - g e n e r a t i o n white f e m a l e s t h a t d e v e l o p e d o n e a c h differential was d e t e r m i n e d a n d t h e race o f t h e p o p u l a t i o n was d e s i g n a t e d . T w e n t y - e i g h t p o p u l a t i o n s were r a c e 3, twelve w e r e race 1, two were race 5, o n e was race 2, a n d o n e was race 4. P o p u l a t i o n s o f races 3 a n d 1 w e r e widely d i s t r i b u t e d in t h e state. In 26 o f t h e 28 race d e t e r m i n a t i o n s , race d e s i g n a t i o n s u s i n g Williams 82 a n d L e e 68 were t h e s a m e , indicating t h a t if L e e 68 is n o t available, Williams 82 m a y b e a suitable a l t e r n a t i v e for r a c e tests d o n e in t h e n o r t h central U n i t e d States. Key words: d i s t r i b u t i o n , Glycine max, Heterodera glycines, n e m a t o d e race, s o y b e a n cyst n e m a t o d e .
T h e soybean cyst nematode Heterodera glycines Ichinohe was first reported in Illinois in 1959 (1). Since then, the nematode has been found in 88 of the 102 counties in the state (4). Races 1, 2, 3, 4, and 5 of H. glycines, as well as some uncharacterized populations, had been reported previously in Illinois (4). These populations were characterized using the race scheme first established by Golden et al. (5) to describe races 1-4 and later expanded to include races 5 and 7 (2,6). T h e scheme employs four soybean differential lines to determine the race of an H. glycines population based on the ability of females to reproduce on the soybean differentials relative to a susceptible standard. Riggs and Schmitt (8) recently expanded the race scheme by designating the 16 races that were theoretically possible when using four soybean differentials. T h e expansion of the race scheme to 16 races provides the means to identify previously unclassified races. T h e objectives of the research reported herein were to clarify the distribution ofH. glycines races in Illinois and to determine whether Williams 82 soybean can be substituted for Received for publication 15 March 1991. J Extension Plant Pathologist, Department of Plant Pathology, University of Illinois, Urbana, IL 61801. 2 Research Plant Pathologist, Crop Protection Research Unit, USDA ARS, Department of Plant Pathology, University of Illinois, Urbana, IL 61801.
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Lee 68 as a standard in race determinations. MATERIALS AND METHODS
Forty-four populations ofH. glycines were collected from sites in 23 Illinois counties during 1989 and 1990. Soil samples from infested fields were obtained from county extension advisers and through the University of Illinois Plant Diagnostic Clinic. Samples ranged in size from 4 to 20 liters of soil. Depending on the date of collection, samples were stored in plastic containers at 5 C for 1-10 months prior to initiating experiments. Cysts were extracted from soil using the wet-sieving technique (3) and were hand-crushed in Syracuse watch glasses c o n t a i n i n g double distilled water. Second-stage juveniles (,]2) and eggs were washed onto a modified Baermann funnel; after 24 hours, J2 and eggs were collected and stored for 2 days at 4 C prior to inoculation. Seeds of the soybean differentials Pickett 71, Peking, PI 88788, and PI 90763 (5) and two standards (Lee 68 and Williams 82) were germinated, and after cotyledons expanded, seedlings were transferred individually into 7.5-cm-d clay pots containing autoclaved sand. Plants were inoculated 2 days later with a mixture of 1,000J2 and eggs in 5 ml of water. Plants were arranged in a completely randomized design and growth in a greenhouse at 22-
Heterodera glycines Races: Sikora, Noel 625 28 C. Replications for individual populations varied from three to six, depending on the amount of inoculum available. One month after inoculation, females were washed off roots and extracted from soil using the gravity-sieving technique with n e s t e d 850-~m-pore a n d 250-t~m-pore sieves. An index (I; 8) was determined for the average number of females that developed on each differential line by dividing the average number of females recovered from the standard and multiplying by 100. A separate value of I was calculated for Lee 68 and for Williams 82. T h e value of I for each plant (experimental unit) was calculated, and the average of all the replications determined the index o f the differential. If I >-- 10, the differential was assigned a +, and if I < 10, the differential was assigned a - . RESULTS
T h e 44 populations o f H. glycines were separated into five distinct groups using the four soybean differentials (Table 1). O f the populations tested using Lee 68 as a standard, 28 (64%) were race 3, 12 (27%) were race 1, two (5%) were race 5, one was race 2 (2%), and one was race 4 (2%). Races 6-16 as described in the expanded race scheme (8) were not identified during the study. T h e 28 populations identified as race 3 were found in 18 of 23 counties surveyed and were distributed in all regions of the state (Fig. 1). T h e i r distribution ranged from the southern tip (Pulaski Co.) to the northern limits (Lee Co. and Whiteside Co.) and from the western (Adams Co.) to eastern (Clark Co., Edgar Co., and Iroquois Co.) borders as well as to the majority of the centrally located counties included in the study. T h e 12 race 1 populations were identified in 10 different counties in the north, central, and west-central regions of the state. T h e two northernmost counties included in the study (Lee Co. and Whiteside Co.) each contained two race 1 populations.
FIG. 1. D i s t r i b u t i o n o f Heterodera glycines races in Illinois, 1 9 8 9 - 1 9 9 0 .
Both race 5 populations were found in adjacent counties (Ford Co. and Iroquois Co.) in the east-central region of the state. Ford Co. was the only county to have three different races (1, 3, and 5). T h e race 2 (Marion Co.) and race 4 (Jefferson Co.) populations were from the south-central region of the state. T h e race 4 population was collected from research microplots at the USDA hematology farm in Urbana, Illinois (Champaign Co.) in October 1989. T h e population was collected originally in Jefferson Co. in 1979 and established on the research farm, where it has been maintained for 11 years. Race determinations for a population were the same for 26 of 28 tests when Lee 68 and Williams 82 were used concurrently
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Supplement to Journal of Nematology, Volume 23, October 1991
TABLe 1. DeVelopmental index for Heterodera glycines populations on four soybean differentials in relation to susceptible soybean standards Lee 68 and Williams 82 and race designation in Illinois, 1989-1990. Developmental index (%)t County and population Adams-26 Adams-42 Champaign-2 Clark-24 Clark-51 Clinton-27 Dewitt-31 Edgar-17 Edgar-28 Ford-14 Ford-22 Ford-29 Gallatin- 12 Greene-18 Grundy-7 Jefferson-54 Iroquois-10 Iroquois-48 Lee-3 Lee-6 Lee-21 Livingston-4 Livingston-36 Livingston-45 Livingston-49 Macon-16 Marion-8 Marion-46 Marshall-15 Marshall-20 Marshall-25 Marshall-38 Mason-19 Mason-41 McLean-40 Monroe-9 Monroe-30 Monroe-44 Pulaski-3 Pulaski-39 Tazewell-13 Whiteside-1 Whiteside-23 Whiteside-35
Pickett 71
Peking
PI 88788
PI 90763
Race:~
L68
W82
L68
W82
L68
W82
L68
W82
L68
W82
0.0 0.0 3.7 1.2 1.5 0.0 6.5 0.0 0.0 13.0 0.0 0.0 0.0 5.0 4.2 52.4 23.4 1.8 3.6 2.1 4.5 0.3 0.0 1.0 0.0 0.0 40.3 0.0 0.7 0.0 2.4 0.8 0.0 0.0 0.0 1.0 0.4 0.0 0.8 0.0 3.3 0.5
0.0
0.0 0.0 3.8 0.0 0.4 0.0 0.0 0.0 0.0 3.9 0.0 0.0 0.0 0.0 4.2 18.0 1.7 0.0 0.0 0.3 0.0 0.8 0.0 0.0 0.0 0.0 25.8 0.0 1.3 0.0 0.0 1.5 0.0 0.0 0.0 0.0 0.0 0.2 0.0 0.0 0.0 0.0
0.0
3.2 30.3 22.6 6.0 6.4 0.0 0.0 6.3 2.9 19.1 10.3 3.3 9.8 12.5 53.1 16.1 32.9 9.0 45.5 41.8 0.0 5.8 4.9 0.0 9.6 6.3 40.2 6.1 6.3 3.5 0.3 0.0 36.4 2.9 6.1 5.0 11,4 2.8 3.3 5.3 13.3 16.6
1.4
0.0 0.0 0.3 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 2.1 15.7 0.7 0.0 0.0 0.0 0.0 0.2 1.5 0.0 0.0 0.0 1.3 0.0 1.0 0.0 2.4 0.0 0.0 0.0 0.0 0.0 0.6 0.0 0.0 0.0 0.0 0.0
0.0
3 1 1 3 3 3 3 3 3 5 1 3 3 1 1 4 5 3 1 1 3 3 3 3 3 3 2 3 3 3 3 3 1 3 3 3 1 3 3 3 1 1
3
1.8
6.9 0.0 0.0 0.0 18.7 0.0 0.0 6.8
22.5 4.9 1.9 1.1 0.0
55.7 0.0 0.5 0.0 5,0 2.3 0.0 0.0 1.0 1.1 0.0 0.5
1.2 0.5
6.9 0.0 0.0 0.0 5.9 0.0 0.0 0.0
1.9 0.0 1.9 1.1 0.0
27.4 0.0 1.1 0.0 0.0 4.6 0.0 0.0 0.0 0.0 1.2 0.0
0.0 0.0
0.0
11.7
39.8 10.8 0.0 0.0 27.6 8.2 16.1 17.2
36.1 81.6 23.7 6.4 8.0
47.4 4.0 5.1 4.4 0.2 0.0 44.8 2.4 5.1 17.5 5.2 4.1
13.3 3.5
8.2
0.8 0.0 0.0 0.0 0.0 0.0 0.0 0.0
1.1 0.0 0.0 0.4 0.0
1.6 0.0 0.8 0.0 5.0 0.0 0.0 0.0 0.0 1.6 0.0 0.0
0.0 0.0
1 1 3 3 5 3 1 1
5 1 1 3 3
2 3 3 3 3 3 1 3 3 1 3 3
1 3
1
t Values are percentage of females that developed on a soybean differential in comparison to Lee 68 (L68, first value) or Williams 82 (W82, second value). z~Race designation according to use of either Lee 68 (L68) or Williams 82 (W82) as the standard.
as standards. I n two cases (Clark-24 a n d Gallatin-12), the p o p u l a t i o n was designated as race 3 w h e n L e e 68 was used as the standard a n d was designated as race 1 when Williams 82 was used. T h e differences in race designation were a t t r i b u t a b l e to val-
ues o f I for PI 88788. F o r Clark-24, I was 6.0 w h e n Lee 68 was the s t a n d a r d a n d 10.8 w h e n Williams 82 was used. F o r Gallatin12, I was 9.8 w h e n Lee 68 was used and 16.1 w h e n Williams 82 was the standard. Substantial differences in I b e t w e e n L e e 68
Heterodera glycines Races: Sikora, Noel 627 a n d Williams 82 w e r e o b s e r v e d for Champaign-2, Lee-3, a n d Lee-6, b u t these differences did n o t affect the o u t c o m e o f the race designations f o r t h e t h r e e populations. F o r the 28 populations, a v e r a g e dev e l o p m e n t o f females on Williams 82 was approximately 91% o f that r e c o r d e d o n Lee 68. DISCUSSION
P r i o r to this study, race 3 was believed to b e the d o m i n a n t race o f H. glycines in Illinois, and the majority o f infestations in Illinois were e i t h e r d e s i g n a t e d as races 3 o r 4 (4). A l t h o u g h races 1,2, 5, and a n u m b e r o f u n d e s c r i b e d populations had b e e n identified, they were n o t distributed widely in the state (4). Based o n the results o f this study, it is a p p a r e n t that race 3, c o m p o s i n g 64% o f the populations tested, is the most c o m m o n race in Illinois. It also is evident that race 1 constitutes a substantial p o r t i o n (27%) o f H. glycines infestations in Illinois. T h e study also showed that populations o f races 2, 4, a n d 5 constitute less t h a n 10% o f the H. glycines infestations in Illinois. Races 6 - 1 6 w e r e not f o u n d d u r i n g this study, indicating that, if p r e s e n t , these races o c c u r in low frequencies. T h e extensive distribution o f race 1 and the a p p a r e n t r e d u c t i o n in f r e q u e n c y o f occ u r r e n c e o f races 3 a n d 4 m a y b e due, in part, to an increased awareness o f the H. glycines p r o b l e m in the state. G r o w e r s a n d c o u n t y advisers are m o r e aware o f the presence o f the n e m a t o d e and may have bec o m e o v e r d e p e n d e n t on the use o f race 3 and 4 resistant cultivars such as Fayette and private lines d e v e l o p e d f r o m it and its parent, L 7 7 - 9 9 4 (7). P r o p e r use o f these cultivars in a r o t a t i o n s c h e m e involving b o t h n o n h o s t crops and H. glycines-susceptible soybean cultivars will r e d u c e the n e m a t o d e p o p u l a t i o n w i t h o u t causing a shift in its g e n e f r e q u e n c y (10). H o w e v e r , c o n t i n u o u s c r o p p i n g o f a resistant cultivar a n d its overuse in a c r o p p i n g sequence can lead to the d e v e l o p m e n t o f a p o p u l a t i o n that can attack the resistant cultivar (4). I n c r e a s e d planting o f cultivars with the PI 88788 source o f resistance may explain the dis-
t r i b u t i o n a n d f r e q u e n c y o f race 1 in Illinois and the r e d u c e d distribution o f races 3 and 4. H o w e v e r , results also suggest that race 1 is m o r e c o m m o n in the n o r t h e r n third o f the state, w h e r e limited planting o f resistant cultivars has occurred. Previous race tests may not have b e e n accurate. T h e level o f resistance to race 1 in cultivars with t h e P e k i n g s o u r c e o f resistance and a d a p t e d to the Midwest was n e v e r e v a l u a t e d critically. T h u s , m o d e r a t e levels o f d e v e l o p m e n t a l indices o n a cultivar such as Franklin may have b e e n a t t r i b u t e d to race 4 w h e n the level o f resistance to race 1 also may have b e e n low. Because t h e r e are few choices for resistance to race 1, additional race det e r m i n a t i o n s for populations f r o m the s o u t h e r n half o f the state are n e e d e d . Mana g e m e n t strategies may n e e d revision if race 1 is widespread. In o r d e r to standardize race tests, it is desirable to use a single s o u r c e o f p u r e seed o f all lines used in the tests (9) a n d to use L e e as the s t a n d a r d c o n t r o l (5,9), b u t L e e a n d L e e 68 are not readily available. Williams 82 is a m a t u r i t y g r o u p III cultivar c o m m o n l y g r o w n in central Illinois that is susceptible to H. glycines. Because o f its availability and t h e g e o g r a p h i c a l area to which it is adapted, Williams 82 has b e e n used as the susceptible s t a n d a r d in place o f L e e 68 in race tests in the n o r t h - c e n t r a l region. Results indicate that w h e n using b o t h cultivars, race d e t e r m i n a t i o n s were in a g r e e m e n t 92% o f t h e time. T h i s would indicate that if seed o f L e e 68 is not available, Williams 82 can b e substituted for L e e 68 as the susceptible s t a n d a r d in race tests in the n o r t h - c e n t r a l U n i t e d States without adversely affecting p r o p e r use o f resistant soybean to m a n a g e H. glycines in the r e g i o n (4,7).
LITERATURE CITED 1. Brewer, F. L. 1981. Special assessment of the soybean cyst nematode Heterodera glycines problem. Joint planning and evaluation staff paper. U.S. Department of Agriculture, Washington, DC. 2. Chen, P. H., D. S. Zhang, and S. Y. Chen. 1987. First report on a new physiological race (race 7) of soybean cyst nematode (Heterodera glycines). Journal
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of Chinese Academy of Agricultural Sciences 20:94 (Abstr.). 3. Cobb, N. A. 1918. Estimating the nema population of soil. Agricultural Technology Circular No. 1, Bureau of Plant Industry, U.S. Department of Agriculture, Washington, DC. 4. Edwards, D. I., G. R. Noel, and E. J. Sikora. 1990. The soybean cyst nematode problem. Illinois Cooperative Extension Service Report on Plant Disease No. 501. University of Illinois, Urbana. 5. Golden, A. M., J. M. Epps, R. D. Riggs, L. A. Duclos, J. A. Fox, and R. L. Bernard. 1970. Terminology and identity of infraspecific forms of the soybean cyst nematode (Heteroderaglycines).Plant Disease Reporter 54:544-546. 6. Inagaki, H. 1979. Race status of five Japanese
populations ofHeteroderaglycines.Japanese Journal of Nematology 9:1-4. 7. Noel, G. R., and E.J. Sikora. 1990. Evaluation of soybeans in maturity groups I-IV for resistance to Heterodera glycines. Supplement to the Journal of Nematology 22:795-799. 8. Riggs, R. D., and D. P. Schmitt. 1988. Complete characterization of the race scheme for Heterodera glycines.Journal of Nematology 20:392-395. 9. Riggs, R. D., D. P. Schmitt, and G. R. Noel. 1988. Variability in race tests with Heteroderaglycines. Journal of Nematology 20:565-572. 10. Triantaphyllou, A.C. 1975. Genetic structure of races of Heteroderaglycinesand inheritance of ability to reproduce on resistant soybeans. Journal of Nematology 7:356-364.
