QTL Mapping Of Oil And Protein Content In Soybean [Glycine Max(L.) Merr.]

Soybean[Glycine max（L.）Merr.]is the major food and economic crop in the world,providing edible oil and plant protein for human life.Quality improvement in soybean is the main objection of soybean breeding.Quantitative trait loci（QTL）mapping and stability analysis of oil and protein soybean are contributed to fully understand the genetic mechanism of these two traits and accelerate the selection process of high-quality varieties.In this study,a mapping population comprised of 196 F_7:8-10 recombinant inbred lines（RILs,Huachun 2×Wayao）was used to plant in four different environments（Guangzhou in 2014,2015 Guangzhou,Guangzhou in 2017,Xintian in 2017）.QTL analysis of oil and protein contents in soybean was conducted using a high-density genetic map and composite interval mapping method（CIM）.Meanwhile,based on GGE-biplot model,screening of good quality lines was performed on the above 196 RIL lines.The main results are as follows:1.The phenotypic variation of oil and protein in four environments was relatively stable.However,variations among RIL lines were narrow for protein content but was wider for oil content.Genotype,environment,and genotype-by-environment interaction（GEI）showed significant differences in oil content and protein content.The broad-sense heritability of oil and protein contents was high with the values of 0.99 and 0.97,respectively.Transgressive segregation was observed in protein and oil traits of the RIL population.There was a significant negative phenotypic correlation between oil and protein contents in each environment.The frequency distribution of these quality-related traits exhibited a skew-normal or normal distribution model with typical quantitative genetic characteristics controlled by multiple genes.2.The high-density genetic linkage map（G.max wm82.a1.v1）constructed with the genotype of Huachun 2×Wayao population was used as a reference map to generate into a corresponding map（G.max wm82.a2.v1）.Finally,a total of 70,000 SNP in the new high-density linkage map were distributed on 20 chromosomes in soybean,which was the same as the reference map.Compared to the reference map,the new map contained 3,413bin markers and spanned 5,400.4 c M with an average distance of 1.58 c M between markers.3.QTL mapping for oil and protein content in soybean was carried out among multiple environments and/or the average data using CIM method over all environments.Twenty QTL for oil contents were identified,10 of which were detected in at least two environments,including one major QTL（q Oil-5-1）with a phenotypic variation of32.53%-54.47%.While sixteen QTL for protein content were detected,8 of which were validated in at least two environments,including two major QTL（q Pro-10-1 and q Pro-14-1）with phenotypic variations of 8.09%-23.33%.According to our analysis of RNA sequencing（RNA-Seq）,16 potential candidate genes screened from three main-effected QTL（q Oil-5-1,q Pro-10-1 and q Pro-14-1）,as well as one novel and stable QTL（q Oil-11-1）,may be involved in the synthesis or metabolism of protein and oil.4.Among the RIL populations,lines 106,39 and 178 had good oil content,line 178 of which had higher stability.Lines 96,4 and 128 possessed good protein content,line 128 of which had higher stability.In 2015,Guangzhou had better discrimination and representativeness for oil and protein stability.