New QTLs For Seed Weight, Minerals, Cysteine and Methionine Concentrations In Soybean.

Nutritional enrichment of plant derived foods by increasing concentrations of important micronutrients such as iron and zinc is a goal of plant scientists. Soybean is a major legume crop and an important source of certain nutrients including minerals. To improve seed nutrient composition in soybean, it is important to understand the underlying genetic basis. The objectives of this study were to (1) identify QTLs associated with (a) N: S ratio in soybean seeds (b) seed sulfur and selenium concentrations and (c) other mineral accumulation in soybean seeds and (2) to test the association between seed weight and  seed mineral concentration of soybean. Three F₅ derived soybean RIL mapping populations from the crosses Williams 82 X DSR-173, Williams 82 X NKS19-90 and Williams 82 X Vinton 81 were used. Some seed mineral concentrations were consistently highly correlated across populations. A striking result was the inverse relationship between N:S ratio and most other minerals, suggesting the possibility of using N:S ratio as an indirect measure of seed mineral concentration in soybean breeding programs. Lack of association between seed weight and seed mineral concentrations suggests the possibility of improving seed mineral concentrations without significant change in seed weight. Forty unique QTLs (including 3 that support previous QTLs) were distributed across 15 chromosomes in the three different populations of soybean for 18 traits that included seed weight, seed mineral concentrations, N:S ratio, and cysteine and methionine concentrations. Using joint linkage anlaysis, we detected nine QTLs (including 2 supporting QTLs) that were not identified in the analysis of each mapping population individually. Some strong QTLs had no obvious candidate genes, offering the possibility of identifying new genes in nutrient/mineral translocation pathways in soybean.