Annual Report of Progress
to the
MISSISSIPPI SOYBEAN PROMOTION BOARD
for 1997

Objectives & Significant Accomplishments

1. Determine the virulence of stem canker isolates collected in Mississippi in 1997.
   
   Weather conditions were not favorable for stem canker in 1997. Two isolates of stem canker were recovered in 1997. Stem canker was observed in the susceptible line J77-339 in a few plants from several of the variety trials. Several isolates were obtained from farmers' fields around Clarksdale. None of these isolates were from varieties resistant to stem canker.
   
   
2. To evaluate varieties submitted for testing in the Mississippi soybean variety trials in 1997 and breeding lines near release for resistance to stem canker.
   
   Results for the Maturity Group IV early and Group IV early Roundup Ready entries are given in Table 1. Results for the Maturity Group IV late and Group IV late Roundup Ready entries are given in Table 2. In field Trial 1, 54% of the entries had an average rating of 1.0 (resistant), 6% had an average rating between 1.1 and 2.0 (moderately resistant) and 40% had an average rating between 2.1 and 5.0 (mod erately susceptible to very susceptible). Results in field Trial 2 and in the greenhouse were similar. In Field Trial One, 30% of the entries had both resistant and susceptible types and were either mixtures or were still segregating. Results in the Group IV, Field Trial 2 and the greenhouse trial were similar.
   
   Results for the Maturity Group V early entries are given in Table 3. Results for the Maturity Group V late entries are given in Table 4. In the Maturity Group V early trial and late field trial 1, 41% of the entries had an average rating of 1.0 (resistant), 35% had an average rating between 1.1 and 2.0 (moderately resistant), an d 24% had a rating between 2.1 and 5.0 (moderately susceptible to very susceptible). Forty-eight percent of the entries had both resistant and susceptible types and were either mixtures or were still segregating. Results in Maturity Group V early Field Tr ial 2 and the greenhouse trial were similar.
   
   Results for the maturity Group V early Roundup Ready entries are given in Table 5. Results for the Maturity Group V late Roundup Ready entries are given in Table 6. In the early and late Maturity Group V Roundup Ready Field Trial 1, 54% of the entries had an average rating of 1.0 (resistant), 12% of the entries had an average rating between 1.1 and 2 (moderately resistant), and 34% had an average rating between 2.1 and 5.0 (moderately susceptible to very susceptible). Thirty-seven percent of the entries had both resistant and susceptible types and were either mixtures or were still segregating. Results in the Maturity Group V early Field Trial 2 were si milar except for the entries TVX 5466RR, DGC 7540RR, and DGC 7550RR. These entries have been retested and are resistant.
   
   Results for the Maturity Group VI entries are given in Table 7. Forty-two percent of the entries had an average rating of 1.0 (resistant), 21% of the entries had an average rating between 1.1 and 2 (moderately resistant), and 37% had an average rating b etween 2.1 and 5.0 (susceptible to very susceptible). Forty-seven percent of the entries had both resistant and susceptible types and were either mixtures or were still segregating.
   
   
3. To evaluate varieties and advanced breeding lines submitted for testing in the Mississippi varietal trials for resistance to Cercospora sojina, frogeye leaf spot), and other disease present in the plots.
   
   Field and greenhouse trials were initiated to evaluate varieties for frogeye leaf spot resistance. Plots were inoculated with the fungus. Weather conditions were favorable for disease development.
   
   Results of the Group IV early frogeye trial are given in Table 8. None of the entries were resistant to frogeye. Only one, Stressland, tested MR in the field trial and I in the field trial. A 4341 was MR in the field trial and MS in the Greenhouse trial. All of the other entries were susceptible. Results of the Group IV early Roundup Ready frogeye trial are given in Table 9. None of the entries were resistant to frogeye and only one, SB-HBK X9746RR tested MR in the field. However, this variety tested S in the greenhouse and may have escaped field inoculation.
   
   Results of the Group IV late frogeye trial are given in Table 10. One entry, TVX 4975, tested resistant in the field. Most entries were susceptible or intermediate in these trials. Results of the Group IV late Roundup Ready frogeye trial are given in Table 11. Two of the entries tested resistant in the field trial. However, these same varieties tested intermediate or moderately susceptible in the greenhouse trial and may have escaped the disease in the field.
   
   Results of the Group V early frogeye trial are given in Table 12. Eight of the entries tested resistant or moderately resistant in the field trials. Results of the Group V early Roundup Ready frogeye trial are given in Table 13. Fifteen of the entries tested resistant in the field trial. Only one in the field trial and six in the greenhouse trial were susceptible to frogeye.
   
   Results of the Group V late frogeye trial are given in Table 14. Ten of the entries were resistant to frogeye in the field trial. Results of the Group V late Roundup Ready frogeye trial are given in Table 15. Eight of the fifteen entries were resistant in the field trial.
   
   There appears to be more resistant to frogeye in the Maturity Group V soybean than in the Group IV soybeans.
   
   
4. Evaluate varieties and advanced breeding lines submitted for testing in the Mississippi varietal trials for resistance or field tolerance to the southern races of Phytophthora sojae.
   
   Results of the 1997 hydroponic trials are given in Table 16 or were reported in the 1996 results. These trials conducted after the field work is finished are still in progress. A large percentage of the varieties are either mixed or still segregating. Res istance and susceptibility varied with the race evaluated.
   
   Personnel periodically rate varietal reaction to soybean diseases occurring in the state variety trials established by MAFES. Periodic visits were made to all of the variety trials throughout the season. Stem canker, frogeye leaf spot, late season cercops ora, and brown spot were sporadic at several locations but the disease intensity was not sufficient to obtain meaningful ratings. To date, 38 isolates have been classified for race. Seven isolates were Race One, from Leflore and Washington Co. Four isolates of Race 2 came from Coahoma Co. One isolate of Race 3 came from Sunflower Co. Thirteen isolates of Race 4 were from Sunflower and Coahoma Co. Seven isolates of Race 10 were from Coahoma, Leflore, and Washington Co. One isolate of Race 7 was from Coahoma Co., and one isolate of Race 17 from Noxubee Co. In addition to the identified races, 23 isolates did not fit any race and may be new races or mixtures. We have not run a large number of the isolates. Further testing is needed to identify the unknown races.

   Soybeans in Mississippi Mississippi Agricultural and Forestry Experiment Station  Mississippi State University Extension Service Division of Agriculture, Forestry and Veterinary Medicine

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