Quantitative trail loci mapping of seed protein and oil composition in a diverse soybean recombinant inbred line population

Soybean [Glycine max (L.) Merr.] is the most widely grown oilseed crop and is an economical source of protein for human and animal consumption. Due to the continuous pursuit for higher seed yield through breeding, and simultaneous expansion of soybean acreage into more northern and western growing environments of the U.S., seed composition has been altered. Seed protein has continually decreased while oil has seen a slight increase as a result of the inter-relationship between seed yield, oil and protein. There is a need to increase yield while maintaining protein levels to keep the US production competitive in global markets. The available genetic diversity for improvement of seed compositional traits is limited as only a few founder genotypes account for the majority of the soybean parentage. A diverse recombinant inbred line (RIL) population from PI479762 / PI567214B with 118 genotypes was developed and phenotyped for seed protein and oil composition across three years and two locations. Quantitative trait loci (QTL) mapping was performed using 5,403 SNPs from the Illumina Infinium BARCSoySNP6K BeadChip using inclusive composite interval mapping (ICIM). Individual location and a multi-environment analysis were used to determine stable QTL associated with protein and oil content. Identified QTL were also colocalized with previously reported QTL to validate or propose novel regions. The single environment analysis revealed marker loci linked to seed oil QTL on Gm 08, 09, 11, and 13, and seed protein QTL on Gm 13. Subsequent analysis across multiple-environments confirmed these QTL and their stability across environments. These QTL will be useful to improve the compositional status of U.S. soybeans while introducing genetic diversity for seed composition traits.