Identification of new QTLs for seed mineral, cysteine, and methionine concentrations in soybean [ Glycine max (L.) Merr.]

Increased concentrations of important nutrients in edible parts of plants could result in biofortified foods. Soybean [ Glycine max (L.) Merr.] is a major legume crop and an important source of certain nutrients, including protein and minerals, in human and animal diets. Understanding the underlying genetic basis of seed composition is crucial to improving seed nutrient composition. In this study we used three soybean recombinant inbred line mapping populations derived from the crosses Williams 82 × DSR-173, Williams 82 × NKS19-90 and Williams 82 × Vinton 81, and constructed a joint linkage map from these populations. Forty quantitative trait loci (QTLs) were detected for 18 traits: seed weight, seed magnesium, sulfur, calcium, manganese, potassium, iron, cobalt, nickel, copper, zinc, selenium, molybdenum, cadmium and arsenic concentrations, total nitrogen:total sulfur (N:S) ratio, cysteine and methionine concentrations. Using the joint linkage map, we detected nine QTLs that were not identified in the individual populations. We identified several candidate genes that might contribute to these traits, including transporters and genes involved in nitrogen and amino acid metabolism. Some strong QTLs had no obvious candidate genes, offering the possibility that subsequent confirmation of these QTLs may result in identification of new genes affecting seed nutrients in soybean. Seed weight and seed mineral concentrations were not highly correlated, suggesting the possibility of improving seed mineral concentrations without significant changes in seed weight. An inverse relationship between N:S ratio and most other minerals suggests the possibility of using N:S ratio as an indirect measure of seed mineral concentration in soybean breeding programs.