Association Analysis And QTL Mapping Of Salt Tolerance In Wild Soybean (Glycine Soja L.) At Germination Stage

Soybean(Glycine max)is a major agricultural grain crop,it has high oil and protein content.Due to its high protein and oil content,soybean is an important cash crop for human diet,animal feeds,and biodiesel.Therefore,the demand for soybean is ever increasing worldwide.At the same time,land salinization area is growing.Soil salinity as a major abiotic stress that threatens the agricultural ecological environment and agriculture sustainability woridwide,it also dose a serious damage to soybean yield.Wild soybean as wild relatives of cultivated soybean,has inborn extensive resistance.Currently,breeding is the main way to improve the salt tolerance of soybean.However,the efficiency of traditional breeding is low because that salt tolerance is a complex trait that is affected by numerous genetic and non-genetic factors.Molecular breeders as a targeted,efficient,and comprehensive strategy can elevate the salt tolerance of soybean.Seed germination is a important stage of soybean,it is the foundation of nutritional growth,ensure the soybeans yield in saline soils,and it's also a sentive stage to salt tolerance.However,little information is about soybean salt tolerance at the germination stage.The objective of this study was to identify the genetic mechanisms of soybean seed germination under salt stress.Use association mapping and QTLmapping methods,this study was to research the soybean salt tolerance of seed germination,and screening the molecular markers associated with soybean salt tolerance in wild soybean,to provide eference for soybean marker-assisted selection breeding.Furthermore,explore the soybean salt-tolerance genes and facilitate the soybean salt tolerance genetic research.Main research results are as follows:1.Combine with the SNP chips genotype data,construct a genetic map which has a total of 1016 SNPs,contains 20 linkage group.The map total length is 2069.13 cM,minimum 20 linkage group length is 40.05 cM,155.55 cM maximum,the minimum mark number is 7,and maximum mark number is 103.The linkage group average length is 103.46 cM,the average distance between mark is 2.04 cM.The construction of a new soybean genetic map and the new SNP markers can effective increase the density of soybean genetic map,and it's also benefit for the soybean genetic studies.2.142 RIL soybean were used in QTL detection with three salt tolerance index,in three environment.With the CIM detection,final 24 QTL were detected,4 QTL associated with relative germination rate,9 QTL associated with relative germination index,11 QTL associated with relative imbibition rate.Among them,1 QTL related three salt resistant indexes in two environment are detected;2 QTL associated with relative germination rate detected in two environments;And part of the QTL controlling two or more salt tolerance traits;4 QTL are reported by previous research,and most of the QTL associated with soybean biomass,root length,etc.lt suggested that co locate of QTL position and characters is a common phenomenon in plant,soybean no exception,so soybean breeding cannot simply consider single target traits.At the same time,of the 24 QTL has 7 significant QTL,but most of the QTL heritability is less than 10%,so these QTLs belong to micro effect QTL.These study help us make a brtter understanding of soybean salt tolerance in seed germination.3.Suggestive SNP-trait associations were identifiedwith 292053 SNPs.,forty-four suggestive SNPs were associated with three salt tolerance indices,and the PVE(henotypic variation explanation)form 18.7%to 45.4%.Amonge the 44 SNPs associated sites,18 SNP was signiicantly associated with STIR,25 SNPs were signiicantly associated with STIGI,21 SNPs was signiicantly associated with STGR,In addition 18 SNPs was also signiicantly associated with STGR and STGI.The SNP identified by association mapping,comparied with the soybean public genitic map and the results of other researchers,found that the two SNPs were formerly researched,and the two SNPs concluded in some main effect QTL,which associated with other traits,these traits are mainly plant height,leaf chlorophyll content,hundred grain weight,plant dry weight and yield traits.And these salt stress SNPs also correlated with other abiotic stress,such as drought stress,indicating that soybean salt tolerance may be linked to other resistance of soybean,they have common genetic mechanisms,the genetic loci may plays an important role in the study of soybean resistance.In addition,3 salt tolerance index correlation analysis results show that salt tolerance SNP or gene widely exist in the soybean,the study of these genes or SNPs,will be conducive to finding soybean salt tolerance gene mining,and breeding of salt tolerant varieties.4.Combine with the results of association mapping and QTL mapping above,we found that there are some SNPs and QTLs located in the same region.The SNP associated with STGI(AX-93698081,2013)in the wild soybean accessions,and the QTLs in the RIL(qSTGI3-1,2013;qSTGR3-l,Average),they located in the same region.In addition,there are three SNPs associated with STGR(AX-93952723,2013;AX-93883783,2013;AX-93952723,AVG)in the wild soybean accessions,with the QTLs in the RIL(qSTIR18-1,qSTGI18-1,qSTIR18-1,2015),they also located in the same region.These QTLs related to different salt tolerance indexs that detected in different years and different populations,it suggested that these QTLs resistant to salt tolerance are conservative in soybean,and play an important role in soybean salt tolerance,worthy of further research.