GWAS and Identification of Candidate Genes Associated with Seed Soluble Sugar Content in Vegetable Soybean

Total soluble sugar (TSS) is an important component in vegetable soybean seeds during the R6 stage and greatly impacts fresh soybean flavor. Increasing the TSS content is thus one of the most important breeding objectives for the creation of high-quality vegetable soybean germplasm. To better understand the genetic basis of the TSS at the R6 stage, we investigated 264 germplasm accessions in two environments. We obtained five associations with 27 significant SNPs using GWAS. The significant SNPs S15_10810881-S15_10843821 and S06_12044239-S06_12048607 were identified in both environments. We then conducted candidate gene analysis and uncovered nine candidate genes as potential regulators of TSS content in vegetable soybean seeds using RT-PCR. These genes may be involved in the regulation of soluble sugar content in soybean seeds. This study provides new knowledge for the understanding of the genetic basis of TSS at the R6 stage and will help improve regulation of TSS in vegetable soybean using molecular breeding.