Location: Crop Genetics Research2011 Annual Report
1a. Objectives (from AD-416)
Determine the inheritance and identify molecular markers linked to genes controlling resistance to Macrophomina phaseolina; identify differential sources of resistance/tolerance to Asian soybean rust and identify molecular markers associated with responsible genes; identify differential sources of resistance/tolerance and associated molecular markers for the Phomopsis/Diaporthe complex; and conserve available genetic diversity in genus Glycine; acquire and characterize new accessions to enhance the southern USDA Soybean Germplasm Collection.
1b. Approach (from AD-416)
Phenotype an F5 derived recombinant inbred (RIL) population segregating for resistance to Macrophomina phaseolina in replicated, multi-location, multi-year field tests, create a molecular map of the RIL population, determine the inheritance of resistance and identify molecular markers linked to resistance loci. Develop populations segregating for resistance to Phakopsora pachyrhizi. Phenotype selected populations in the field in Paraguay, determine whether resistance loci represent new genes, identify molecular markers linked to any new resistance loci, develop RIL populations as needed, and select for enhanced resistant germplasm. Evaluate lines identified and evaluated in Paraguay in the quarantine facility at Stoneville against US and Mississippi ASR isolates. Screen selected lines from the USDA-ARS germplasm collection for resistance to Phomopsis seed decay (PSD). Create molecular mapping populations, determine whether resistance loci represent new genes, identify linked molecular markers, and determine the inheritance of any new resistance genes. Incorporate novel resistance genes into germplasm readily suitable for use in the breeding industry. Characterize, pure-line, maintain purity, and increase seed of the approximately 6,500 MG V-VIII accessions of the USDA-ARS Soybean Germplasm Collection grown at Stoneville, MS. Submit pure-lined and detailed characterization of new accessions to the collection. Provide quality seed to the collection for use by soybean researchers worldwide and to maintain viable seed in the collection.
3. Progress Report
The research of this project is focused on reducing soybean yield losses from disease through genetic improvement. Three diseases (charcoal rot, soybean rust, and Phomopsis seed decay) are targeted in the research which is proceeding according to plan. The research involves field studies both in the U.S.A. (charcoal rot and Phomopsis) and in Paraguay (soybean rust). Important soybean rust experiments were also conducted in the Quarantine Facility at Stoneville, MS. Extensive molecular marker assays, pathology assays, and seed quality assays were conducted in the laboratory facilities of the project. In addition to the research program, the project also maintains the southern portion of the USDA-ARS Soybean Germplasm Collection. We developed a breeding line that has the same level of resistance to charcoal rot as DT97-4290 (one of the first lines released with charcoal rot resistance). However, the new breeding line matures approximately 2 weeks earlier than DT97-4290, and averaged over 6 bu/A greater yield at Stoneville, MS. Three breeding lines with resistance to Asian Soybean rust have been developed. In a yield trial under heavy rust pressure in Paraguay, the lines lost as little as 8% of their yield as compared to susceptible lines with yield losses of up to 40%. Additionally, segregating populations created from a soybean line that we previously identified as rust resistant in Paraguay and as resistant to several domestic isolates, were screened at Capitan Miranda Paraguay, at the Quarantine Facility at Stoneville, MS, and at the Quarantine facility at Ft. Detrick, MD. Mapping the resistance genes in these populations is currently nearing completion. Research screening germplasm for resistance to phomopsis seed decay is on-going and potential new resistant lines have been identified and results confirmed. Twenty-seven new breeding lines with high germination and 12 soybean cultivars/accessions were evaluated for germination, vigor, hardseededness, Phomopsis seed decay, and seed composition after timely and delayed harvests. Seed yield and seed coat wrinkling were evaluated at harvest maturity. The best high-yielding high-germination breeding line yielded 59 bu/A and had a seed germination of 96%. Further, this line maintained germination above 90% (94%) even after a two-week harvest delay. By comparison, other high-yielding cultivars had reductions in germination of up to 44%. In terms of Phomopsis seed infection, the best breeding line had between 2.7 and 11% seed infection whereas comparable cultivars had up to 48% seed infection. Overall, experiments are proceeding according to plan. For the Germplasm Collection work, seed increase plots were established and are being maintained appropriately.
1. Identification of a new soybean rust resistance allele. Genetic resistance to soybean rust in PI 567099A was identified at or near the Rpp3 locus. The resistance was determined to be recessive. PI 567099A provides geneticists and breeders with a new source of resistance to soybean rust which can be useful in breeding programs as well as in understanding the nature of resistance.
2. Identification of plant introductions resistant to Phomopsis seed decay. New sources of resistance to Phomopsis seed decay have been identified. These soybean lines have been incorporated into soybean breeding programs in Arkansas, Illinois, and Mississippi to develop improved cultivars with high yield and disease resistance. Genetic studies are underway to identify the inheritance of the resistance.
Qian, H., Li, S., Xu, Y., Li, C., Sun, Y. 2011. Assessment of the effects of Hirsutella minnesotensis on Soybean Cyst Nematode and growth of soybean. Soybean Science. 30(2):266-271.