Identification of Drought-Tolerance Genes in the Germination Stage of Soybean

SIMPLE SUMMARY: Drought stress inhibits seed germination, making it one of the primary environmental factors adversely affecting food security. Soybean is more sensitive to drought than other food crops, especially in germination stage. The purpose of our research is to identify the loci related to drought tolerance in soybean during germination. We used 410 soybean accessions to induce drought at germination stage by PEG, and conducted genome-wide association study. A total of 26 SNPs were found to be related to drought tolerance, and there were nine SNP markers located in or adjacent to (within 500 kb) previously reported drought tolerance QTLs. These SNP led to our identification of 41 candidate genes related to drought tolerance. The current analyses provide information and tools for subsequent studies and breeding programs for improving drought tolerance. ABSTRACT: Drought stress influences the vigor of plant seeds and inhibits seed germination, making it one of the primary environmental factors adversely affecting food security. The seed germination stage is critical to ensuring the growth and productivity of soybeans in soils prone to drought conditions. We here examined the genetic diversity and drought-tolerance phenotypes of 410 accessions of a germplasm diversity panel for soybean and conducted quantitative genetics analyses to identify loci associated with drought tolerance of seed germination. We uncovered significant differences among the diverse genotypes for four growth indices and five drought-tolerance indices, which revealed abundant variation among genotypes, upon drought stress, and for genotype × treatment effects. We also used 158,327 SNP markers and performed GWAS for the drought-related traits. Our data met the conditions (PCA + K) for using a mixed linear model in TASSEL, and we thus identified 26 SNPs associated with drought tolerance indices for germination stage distributed across 10 chromosomes. Nine SNP sites, including, for example, Gm20_34956219 and Gm20_36902659, were associated with two or more phenotypic indices, and there were nine SNP markers located in or adjacent to (within 500 kb) previously reported drought tolerance QTLs. These SNPs led to our identification of 41 candidate genes related to drought tolerance in the germination stage. The results of our study contribute to a deeper understanding of the genetic mechanisms underlying drought tolerance in soybeans at the germination stage, thereby providing a molecular basis for identifying useful soybean germplasm for breeding new drought-tolerant varieties.