BSA-Seq Identification Of Soybean Salt-Tolerant QTLs And Its Application

Soybean（Glycine max）is the most important oil crop as well as an important source of food and protein worldwide.At present,China’s local soybean supply is desperately in short,soybean supply mainly rely on foreign imports.In order to meet the domestic demands,the state began to accelerate the molecular breeding process of soybean to promote the modernization of soybean agriculture.Soil salinization is one of the main limiting factors of China’s current agricultural development,and the production of soybeans is seriously restricted by soil salinity.The development of salt-tolerant adaptable varieties has been one of the main goals of soybean breeding.Identification of QTL/genes that contribute to salt tolerance and development of associated molecular markers have become effective ways to promote soybean breeding.In present study,the salt hyper-sensitive variety Dong nong 50and the middle tolerant variety Williams 82 were used as materials to rapidly locate salt-sensitive genes by developing F₂ mapping populations and performing Bulked Segregant Analysis（BSA）.We further narrowed the association region by linkage disequilibrium（LD）analysis and gene expression analysis.Selected candidates genes were further functional validated using hairy root system.The QTL/gene detected in this study can be further fine-mapped or used to develop molecular markers to accelerate breeding of salt-tolerant soybeans.The main findings are as follows:（1）The survival rates of Williams 82 and Dong nong 50 were significantly different under four salt concentrations,and the survival rates decreased gradually with the increase of salt concentrations.The two exhibited the most significant difference under 150 m M Na Cl treatment,which was suitable for the evaluation of soybean salt sensitivity.Therefore,150m M Na Cl concentration was selected for phenotypic evaluation of F₂ generation population and subsequent tests.（2）224 Williams 82×Dongnong 50 F₂ line show dinstict salt sensitiivites under salt stress treatment,and the distribution frequency follows a typical normal distribution.The salt susceptibility and tolerant pool was constructed based on their survival rate and used for BSA-Seq.A total of 7 QTLs associated with salt tolerance were identified,and chromosome13 was identified as the primary candidate region for salt tolerance genes,spanding 3.5Mb genomic region,containing 440 candidate genes.The most significant associated SNP was located at 36397Kb-36467Kb.（3）A salt-responsive gene Glyma.13G267700 was identified based on the combination of LD analysis,functional annotation and its expression changes in response to salt stress.Sequence analysis and functional annotation indicated that this gene encodes a WRKY-type transcription factor,which is a homologue of Arabidopsis At WRKY70.（4）Subcellular localization indicated that the protein（GmWRKY123）was localized in the nucleus.The salt tolerance of Dongnong 50 was greatly improved by over-expression of this gene through hairy root transformation.