Genome-wide association studies for sulfur-containing amino acids in soybean seeds

Soybean provides abundant dietary proteins for humans and livestock. However, the low content of sulfur-containing amino acids [SAA, including methionine (Met) and cysteine (Cys)] in soybean protein limits the quality and prevents it from becoming an ideal food and feed ingredient. Thus, the exploration of novel high-SAA soybean germplasm and identification of related genes is necessary. In this study, a genome-wide association study (GWAS) was conducted for Cys, Met and SAA in 165 soybean materials genotyped with a high-density SNP array. A total of 138 significant SNPs associated with three traits were identified. Moreover, one SNP on chromosome 7 was identified in three environments. Glyma.07g175700 and Glyma.07g176000 at the LD of AX-94036794 were considered candidate genes. Quantitative real-time PCR showed that different expression levels of these genes were observed in high-SAA and low-SAA material, which suggested that these two genes may be involved in SAA synthesis. These results will help to increase our understanding of the genetic mechanisms of SAA and improve nutritional quality through molecular marker-assisted selection breeding in soybeans.