Cloning Of Gene Controlling Thorns And Genetic Analysis Of Heading Trait In Mustard

Mustard?Brassica juncea?is an important species belonging to Brassica Crops of Cruciferae.There are many kinds of mustard with a variety of special agronomic traits,and it has important economic value.Trichome is generally distributed on the above-ground parts of plants,and affects the transpiration of plants.Heading is a unique agronomic trait of vegetables,which has the advantages of convenient transportation and durable storage.In this study,we constructed F₂segregating populations,and used the method of BSR-seq?BSA+RNA-seq?to map genes controlling heading and thorns in mustard.The results are as following:1. Research on the trait of thornsOur laboratory had constructed an F₂population derived from as cross between GRE102?no thorns on abaxial leaf vein?and RT104?with thorns on abaxial leaf vein?.A total of 132 F₂individuals were phenotyped,and thorny plants and thornless plants had a raito of 106:26??²=1.952,P=0.2?.The result of BSR-seq showed that the thorns were controlled by a single locus primary mapping suggested that the controlling gene was located between 54.76-58.54 Mb of chromosome B02.Then additional 2222 individuals were used to fine map the candidate gene.Finally,it was mapped in a region of 117 Kb.Through collinearity analysis with the Arabidopsis genome,a gene homologues to GL1?Bju GL1?,which controls trichome development in Arabidopsis,is considered as the causal gene for thorn polymorphism in mustard.The GL1 homologue is not expressed in the thornless parent but expressed in the thorny parent.2. Genetic analysis of heading in mustardAn F₂population was derived from cross between SON101?loose-leaf?and LF101?heading?.BSR-seq was used to identify loci controlling the heading trait in this population.Consequently,a total of three loci associated with heading phenotype were identified,which are located on chromosome B04,B05 and B08,respectively.Molecular markers were used to screen for individuals that are heterozygous at a target locus and homozygous for other loci,and the chosen individuals were selfed to generate a single-locus segregating population.Only two F_3:4populations heterozygous on chromosome B04 were found to segregate heading trait.According to the peak position of SNP-Index plot and the distribution of SNP delta value in this region,it was speculated that this gene was likely to be located in the 18.45-22.15 Mb region on B04 chromosome.Functional annotation was done on the differentially expressed genes in the candidate region,and three genes with SNP differences were selected as candidate genes controlling heading in mustard:MYB47,CDPK1 and APC8.The results on the genetics of thorns will be useful for breeding of thorn-free cultivars and contribute good materials for studies on cell fate.The results on genetics of heading in mustard in this study provided important materials for future cloning of genes controlling heading and its molecular mechanism in mustard.The identified loci will be useful for breeding of heading mustard.