Quantitative trait locus analysis of seed sulfur-containing amino acids in two recombinant inbred line populations of soybean

Soybean (Glycine max (L.) Merr.) is a major source of plant protein for humans and livestock. Deficiency of sulfur-containing amino acids (cysteine and methionine) in soybean protein is a main limitation of soybean meal as an animal feed ingredient. The objectives of this study were to identify and validate quantitative trait loci (QTLs) associated with cysteine and methionine contents in two recombinant inbred line (RIL) populations, and to analyze the genetic effects of individual QTLs and QTL combinations in soybean. Both the mapping population of SD02-4-59 x A02-381100 and validation population of SD02-911 x SD00-1501 were evaluated for cysteine and methionine contents in multiple environments. Correlation analysis indicated that there was a highly positive correlation between cysteine and methionine contents. Significant positive correlations were also observed between the sulfur-containing amino acid contents and protein content. In the mapping population, eight QTLs for both cysteine and methionine contents were consistently detected in any individual environment and the average data over all three environments. Three of these QTLs were confirmed in the validation population. A comparison with the previous studies indicated that most of the genomic regions linked to the QTLs for the sulfur-containing amino acids were also associated with protein content. Cumulative effects of multiple QTLs for the traits were significant in both populations. This information should be useful for the improvement of the levels of protein and amino acids in soybean seeds.