Identification of genes for drought resistance and prediction of gene candidates in soybean seedlings based on linkage and association mapping

Drought is one of the primary abiotic stress factors affecting the yield,growth,and development of soybeans.In extreme cases,drought can reduce yield by more than 50%.The seedling stage is an important determinant of soybean growth:the number and vigor of seedlings will affect growth and yield at harvest.Therefore,it is important to study the drought resistance of soybean seedlings.In this study,a recombinant inbred line(RIL)population comprising 234 F_(6:10)lines(derived from Zhonghuang35×Jindou 21)and a panel of 259 soybean accessions was subjected to drought conditions to identify the effects on phenotypic traits under these conditions.Using a genetic map constructed by single nucleotide polymorphism(SNPs)markers,18 quantitative trait loci(QTL)on 7 soybean chromosomes were identified in two environments.This included 9 QTL clusters identified in the RIL population.Fifty-three QTL were identified in 19 soybean chromosomes by genome-wide association analysis(GWAS)in the panel of accessions,including 69 significant SNPs(-log_(10)(P)≥3.97).A combination of the two populations revealed that two SNPs(-log_(10)(P)≥3.0)fell within two of the QTL(qPH7-4 and qPH7-6)confidence intervals.We not only re-located several previously reported drought-resistance genes in soybean and other crops but also identified several non-synonymous stress-related mutation site differences between the two parents,involving Glyma.07 g093000,Glyma.07 g093200,Glyma.07 g094100 and Glyma.07 g094200.One previously unreported new gene related to drought stress,Glyma.07 g094200,was found by regional association analysis.The significant SNP CHR7-17619(G/T)was within an exon of the Glyma.07 g094200 gene.In the RIL population,the DSP value of the"T"allele of CHR7-17619 was significantly(P<0.05)larger than the"G"allele in different environments.The results of our study lay the groundwork for cloning and molecular marker-assisted selection of droughtresistance genes in soybeans at the seedling stage.