Location: Crop Genetics Research2010 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 (MG V-VIII). Field studies evaluating and mapping charcoal rot resistance were completed in FY 2010. Nearly 2,000 stem/root samples were processed and analyzed for charcoal rot resistance. Results of these experiments are expected to provide information on charcoal rot resistance inheritance and the genomic location of genetic factors controlling resistance. Additional genetic populations segregating for charcoal rot resistance are being developed. Over 3,000 single-row plots were evaluated for rust reaction in Capitan Miranda, Paraguay. These plots represented multiple F2, F2:3, and recombinant inbred populations and breeding lines. Nearly 500 breeding lines were found to have resistance to rust and recommended for further trials. One resistant line is scheduled for release, with sales to soybean farmers projected for 2012. Breeding lines were confirmed to have various resistance genes including Rpp1b, Rpp2, Rpp3, and a yet-to-be named new gene. Selected breeding lines were included in this year’s yield trials. An F2:3 population was screened at the quarantine facility in Stoneville using Mississippi isolates. Additional resistant lines identified in China were screened using U.S. isolates. Several lines with resistance to both Chinese and American rust isolates were identified. For the Phomopsis seed decay research a two-year field study was completed characterizing the resistance of selected putative resistant lines. Additionally, a segregating population was phenotyped for Phomopsis resistance and molecular marker analysis is underway to identify resistance loci. Overall, experiments are proceeding according to plan. For the Germplasm Collection work, seed increase plots were established and are being maintained appropriately. Rust research is being done in cooperation with the Camara Paraguaya de Exportadores de Cereales y Oleaginosasm, AGREEMENT NO: 58-0206-5-F176. Other research is being conducted with scientists at other institutions including: 6402-21220-010-08R, Screening Germplasm and Breeding for Resistance to Phomopsis Seed Decay in Soybean (USB# 9261); 6402-21220-010-05R, Identification and Utilization of Exotic Germplasm to Improve Soybean Productivity; 6402-21220-010-06R, Genetics and Mapping of Genetic Inheritance of Charcoal Rot Resistance; and 6402-21220-010-07R, Coupling High Throughput Genetic and Phenotypic Information for Yield Enhancement. Separate reports present progress under these agreements.
1. Release of Disease-Resistant Soybean Germplasm DS-880. Soybean diseases cause severe yield losses and loss of income to soybean producers all over the world. The most cost-effective and environmentally-friendly method to control such diseases is through the use of disease-resistant cultivars. ARS researchers at Stoneville, MS, released DS-880 soybean, which has high-yield potential and resistance to soybean cyst nematode, reniform nematode, charcoal rot, stem canker, and sudden death syndrome. Per request, seed was distributed to soybean scientists from Missouri, Arkansas, Minnesota, Virginia, Maryland, Tennessee, Mississippi and Kansas. This release can directly impact reduction in yield losses by its direct use by producers and through its use as a parent in developing new disease-resistant cultivars.