2012 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 germplasm 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.
All objectives of this project are fully met. We have identified two genomic locations for novel quantitative trait loci for soybean cyst nematode resistance. The MG-II food-type soybean aphid resistant germplasm to be released this summer is high-yielding and has no yield drag associated with the Rag2 resistance gene. This line also has powdery mildew resistance. Mapping of soybean aphid resistance genes in PI 567324 was completed. All resistant genes were validated in independent backcross populations. Phenotyping for partial resistance to bean pod mottle virus is underway for two recombinant inbred lines populations, each with 184 progeny lines. High-protein high-yield soybean lines are being yield tested in multiple locations in multiple states in 2012. These lines show 2-4% increase in protein without any associated loss of yield indicating a breakthrough in the historical negative association between protein content and seed yield of soybean. Fine mapping of the Rag2 gene is ahead of schedule and is expected to be completed by the end of 2012.
In addition to our project objectives, we are working to develop soybean lines with high-yield with exotic pedigree, resistance to frogeye leaf spot, beetle resistance, low phytate, low linolenic acid, high oleic acid. A number of MG II –III high-yielding lines with 13-25% exotic pedigree has shown 10-15% yield advantage compared over the check cultivars. Such a jump in yield gain, if confirmed, would be exceptional for soybean. Five such lines are in the northern regional testing in 2012. The breeding lines with frogeye leaf spot are being evaluated for yield and other agronomic traits against check cultivars in Wooster in 2012. The breeding lines for other traits are in their early generations (F1-F4).
Soybean genes with soybean aphid resistance. The soybean aphid is the number one insect pest of soybean in the U.S. and worldwide. The damage to U.S. soybean crop by the soybean aphid is estimated to be more than two billion dollars. Host plant resistance is a sustainable method for controlling the soybean aphid. ARS scientists in Wooster, OH in collaboration with researchers at The Ohio State University, mapped three soybean aphid resistant loci (genes) in a soybean plant introduction from China. These new genes will be useful in breeding soybean aphid resistant cultivars for U.S. growers.
Fine mapping of a powdery mildew resistant gene. Powdery mildew is a disease of soybean in north central soybean growing regions of U.S. and in Canada. Under favorable environmental conditions this disease can reduce the yield of susceptible cultivars by 20%. ARS scientists in Ohio, fine mapped a powdery mildew resistance gene on soybean chromosome 16 and developed three DNA markers for marker assisted selection of this gene. These molecular markers will be useful for marker assisted breeding for powdery mildew resistant soybeans. Public and private soybean breeders will benefit from this discovery.
High-protein high-yielding soybean lines. Breeding soybeans with high-protein and high meal value (=48%) is a major priority of the U.S. soybean producers. ARS researchers in Wooster, OH have developed several high-protein (=44%) high-yielding conventional soybean lines with meal value exceeding 48%. These lines have been yield tested in multiple environments over multiple years. They have 2-4% higher protein contents than the check cultivars with same or better yield than the checks. Such soybean lines with high meal value will increase the profitability of U.S. soybeans and make them more competitive in the international markets.
Jun, T., Mian, R.M., Michel, A.P. 2012. Genetic mapping revealed two loci for soybean aphid resistance in PI 567301B. Journal of Theoretical and Applied Genetics. 124(1):13-22.
Orantes, L.C., Zhang, W., Mian, R.M., Michel, A.P. 2012. Maintaining genetic diversity and population panmixia through dispersal and not gene flow in a Holocyclic heteroecious aphid species. Heredity. 109(2):127-134.
Jun, T., Mian, R.M., Freewalt, K.R., Mittapalli, O., Michel, A.P. 2011. Development of genic-SSR markers from soybean aphid sequences generated by high-throughput sequencing of cDNA library. Journal of Applied Entomology. 136:614-625.
Jun, T., Mian, R.M., Kang, S., Michel, A.P. 2012. Genetic mapping of the powdery mildew resistance gene in soybean PI 567301B. Journal of Theoretical and Applied Genetics. DOI 10.1007/s00122-012-1902-y.