The Mapping Of A Novel QTL QNE1 For Flowering Time And Genetic Analysis Of Its Regulation On Branching In Soybean

Maturity and plant type are important agronomic traits affecting the yield of soybean.Flowering time and maturity are highly associated with cultivation area of a given cultivar.Plant types of soybean cultivar,especially branching number,determines suitable plant density for the highest seed yield.In this study,99 F₂ plants derived from a cross between Suinong10?E1/e2/e3T/E4?and Iwaheme?E1/e2/e3T/e4-kam?,were genotyped using Illumina SoySNP8 k iSelect BeadChip.We mapped a new major QTL?quantitative trait loci?near E1,referred as to QNE1?major QTL Near E1?for flowering time and a branch-related QTL.Using recombinants and their progenies identified from F₂:3 and F₂:4 populations,QNE1 region was narrowed down.In addition,genetic relation between the maturity loci and plant type,especially branching was analyzed.Based on genotypic and phenotypic data of the F₂ population,a new QTL for flowering time was mapped to near E1 on chromosome 6.Furthermore,12 recombinants identified from 801 individuals of F₂:3 population were used for fine-mapping.The QTL was narrowed down to an about 2.37 MB region between18883704 and 21251562,in which 93 genes were annotated with coding regions of 3genes showing polymorphic between Suinong10 and Iwaheme.In order to further perform fine-mapping,20 recombinants of the region of 18883704—21251562 were identified from 1728 individuals of F₂:4 population of heterozygous genotype.Based on association analysis between genotypes and phenotypes,the region of QNE1 was further delimited to 18883704—19395996,including 2 candidate genes whose coding region showed polymorphic.We analyzed the effects of E4 or QNE1 on branching number.In Suinong10×Iwaheme population,E4 genotype had substantially more numbers of branch thane4-kam genotype.Meanwhile,QNE1 also had some genetic effects on branching although not stastically significant.We identified a new QTL for branching number on chromosome 2,with LOD of3.25 and the phenotypic contribution ratio of 15.08%.However,we failed to validate this QTL in the F₂:3 subpopulation,which may be ascribed to the fact that the QTL for branching number was rather small,and the environmental effects on branching number were so predominant.Therefore,more subpopulations are needed to test the authenticity of this QTL.