Location: Corn, Soybean and Wheat Quality Research2009 Annual Report
1a. Objectives (from AD-416)
1. Identify novel quantitative trait loci (QTL) for soybean cyst nematode (SCN) resistance. 2. Develop soybean germplasm with resistance to soybean aphids and map soybean aphid resistance genes. 3. Identify QTL for partial resistance of soybean to Bean pod mottle virus (BPMV). 4. Develop soybean germplasm with high seed-protein content.
1b. Approach (from AD-416)
Genes involved in disease and insect resistance and other target traits will be identified through molecular mapping. Segregating mapping populations will be developed for all target traits. The genes will be tagged with DNA markers to permit incorporation into advanced soybean germplasm. Molecular markers will be identified to facilitate marker-assisted selection of enhanced germplasm. Appropriate methods and technology will be identified or developed to facilitate gene identification and mapping. Soybean germplasms with resistance or tolerance to soybean aphid and high-protein will be developed through a combination of the conventional and marker assisted plant breeding approaches. Virus identification and detection procedures will be developed, and sources of partial resistance to bean pod mottle virus will be identified by greenhouse and laboratory screenings of plant introductions.
3. Progress Report
Following identification of the Ohio biotype of soybean aphid and the Rag2 gene in PI 243540 by ARS scientists in Wooster, Ohio in 2007, we have made fast progress in breeding for soybean aphid resistant germplasm. Advanced breeding lines are being yield-tested at four locations in Ohio in 2009 and germplasm may be ready for release in 2010. Two new germplasm with beetle resistance are being evaluated for the second year in the field in 2009 and germplasm may be ready for release in 2010. In collaboration with Department of Entomology at Ohio State University, we developed DNA markers for genotyping of soybean aphid biotypes. Two recombinant inbred populations (RIL) for mapping partial resistance to soybean aphids were advanced to the F6 generation. Four RIL populations for mapping partial resistance to Phytophthora stem and root rot were advanced to the F8 generation. Molecular mapping for identification of genes for partial resistance to soybean aphids and phytophthora stem and root rot are underway. Four populations for mapping partial resistance to Bean pod mottle virus were advanced to the F3 generation. A study is underway to test the efficiency of soybean aphid in transmitting various viruses. Seeds of high-protein, high-yield F5 lines having >45% seed-protein are being increased for multi-state evaluation in 2010
1. Developed DNA marker and detached leaf assays for identification of soybean aphid biotypes In less than 10 years since its accidental introduction in USA, the soybean aphid has become the number one insect pest of soybean in North America. More than 80% soybean fields in North America are now at risk of being infested with soybean aphids. In addition to its rapid expansion to a large geographic area, soybean aphids are also quickly evolving into new more virulent forms (called biotypes) that can break newly discovered aphid resistance genes in soybean (e.g., Rag1). U.S. soybean growers need to understand the geographic distribution and movement patterns of soybean aphid biotypes in order to select the best aphid resistant soybean cultivars to grow in their farms. ARS scientists in Wooster, in collaboration with the scientists in the Department of Entomology at The Ohio State University, have developed DNA markers that allow us to differentiate among visually identical soybean aphid biotypes for the first time. They have also developed a detached leaf assay to characterize the ability of soybean aphid biotypes to feed on soybeans carrying different resistance genes. The DNA markers and detached leaf assay are currently being used to identify the biotypes of soybean aphids collected from growers’ fields in Ohio and neighboring states. The information on the distribution of aphid biotypes for each state will help soybean growers decide which aphid resistant soybean cultivars to use.
5. Significant Activities that Support Special Target Populations
The aphid resistant soybean lines we are developing will be useful for the small organic growers in northern Ohio.
Mian, R.M., Bond, J., Joobeur, T., Mengistu, A., Weibold, W., Grover, S., Wrather, A. 2009. Identification of Soybean Genotypes Resistant to Cercospora sojina by Field Screening and Molecular Markers. Plant Disease. 93:408-411.