Location: Corn, Soybean and Wheat Quality Research2011 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
Most objectives of this project are fully met or ahead of schedule. We will complete development of soybean aphid resistant line ahead of schedule by releasing germplasm at the end of 2011. The aphid resistant germplasm is high-yielding and no yield drag associated with the resistance gene has been seen. The BC4F4 lines with Rag2 gene are being field tested at multiple locations in 2011 for the third year. Mapping of soybean aphid resistance genes in PI 567301B was completed and two new genes were mapped and a manuscript on this research was recently accepted for publication in Theoretical and Applied Genetics. We have also identified 4 quantitative trait loci (QTLs) for soybean aphid resistance in PI 567324 and fine mapping of these QTLs are in progress. High-protein high-yield soybean lines are being tested in multiple locations in Ohio one year ahead of schedule. These lines show 2-4% increase in protein without any associated loss of yield indicating a break though in the historical negative association between protein content and seed yield of soybean. Fine mapping of the Rag2 gene has started 3 years ahead of schedule and are expected to be completed by the end of 2011. In addition to our project plan objectives, we are working to develop soybean lines with resistance to frogeye leaf spot, beetle resistance, low phytate, low linolenic acid, high oleic acid, and high yield from exotic sources. The breeding lines with frogeye leaf spot are being evaluated for yield and other agronomic traits against check cultivars in Wooster in 2011. One breeding line with beetle resistance will be released by the end of 2011. Breeding lines with high-yield are being tested in four locations in Ohio in 2011.
1. A new gene for soybean aphid resistance. The soybean aphid is the number one insect pest of soybean in the USA and worldwide. Damage caused by the aphid to 2010 US soybean crop was estimated to be more than a billion dollars. Host plant resistance is the most desirable method for controlling the soybean aphid. ARS scientists in Wooster, OH, in collaboration with researchers in Department of Entomology at The Ohio State University, mapped a new soybean aphid resistance gene (named Rag5) from soybean PI 567301B. The results of this research were published in a refereed journal and seed of resistant soybean lines has been made available to public and private soybean breeders and researchers. This new gene will contribute to sustainable control of the soybean aphid to increase profitability of soybean growers in the USA.
2. High-yield soybean lines. The genetic basis of modern US soybean cultivars is very narrow. To continue to increase soybean productivity in the USA, it is necessary to broaden the genetic base by incorporation of new yield genes from plant introductions. ARS researchers in Wooster, OH, developed 10 high-yielding soybean breeding lines with yield genes from USDA, ARS' exotic germplasm collections. These high-yielding soybeans will be useful to increase profitability of US soybean growers and contribute to food security.
3. EST-SSR markers from soybean aphid transcripts. Soybean aphid is the most damaging insect pest of soybean. Three new soybean aphid types capable of overcoming the resistance conferred by newly identified soybean genes have been identified in the USA. There is an urgent need for rapid identification of the soybean aphid types for successful implementation of integrated pest management for the aphid. The simple sequence repeats (SSRs) are very useful markers to genetically differentiate the different aphid types. ARS scientists in Wooster, OH, in collaboration with researchers in Department of Entomology at The Ohio State University have developed 240 EST-SSR markers from expressed sequence tags (ESTs) of soybean aphid. These SSR markers will enable researchers to conduct molecular and genetic studies of the soybean aphids and create an aphid type distribution map in the USA. Such a map is critical for growers to decide which aphid resistant soybean cultivars to grow in their farms.Jun, T., Michel, A.P., Mian, R.M. 2011. Development of soybean aphid genomic SSR markers using next generation sequencing. Genome. 54:360-367.