QTL Mapping For Brach Angle And Analysis Of Candidate Genes In Brassica Napus L.

In recent years,our country’s grain and oil self-sufficiency rate is less than 40%.Involuntary,it is necessary to develop rapeseed industry for ensure the safety of grain and oil strategy.The rapeseed’s yield and mechanization have been low.So,the plant breeding is needed to promote the upgrading of the rapeseed.As is well known,Branch angle,which is an important trait associated with the morphology of ideotype,the compact branches varieties are conducive to increasing planting dense,mechanized harvesting,production and the development of the rapeseed.Therefore,the study on the branching angle can lay the foundation for the plant breeding,the yield and efficiency of B.napus.In this study,two materials with significant differences in plant height and branching angle were selected as the parental material（09GY45,HY16）.The parents09GY45（P₁）,HY16（P₂）and their hybrid F₁ materials were planted in Yangling and Qianxian in 2020.Similarly,P₁,P₂,F₁,and F_2:3 were planted in 2021.To investigate phenotypic traits（branch angle,plant height,main inflorescence length,number of branches,first valid branch height）at the maturity stage.Analysis of the genetic basis of plant height and branch angle.Branch angle related traits were identified by the SSR molecular markers and BSA.The result is as follows:1.Analysis the genetic of branch angle-related traits.The analysis model was used to reveal the genetic information of the four generations（P₁,P₂,F₁,F₂）population in Yangling and Qianxian.The results showed that the inheritance of effective branch height was in line with the two-pair additive main gene inheritance（B-4）,and the main gene heritability of branch angle was 67.81%,41.84%,and the main gene heritability of plant height was 49.96%,and 79.19%,main inflorescence length main gene heritability was 75.62%and 59.36%,primary effective branch height main gene heritability was 59.83%（Yangling）,indicating that these traits have high heritability and with little contribution from environmental factors.2.QTL mapping based on SSR molecular markersWe investigate the branch angle of F₂ and F_2:3 generations,the segregating generations F₂ was verified by SSR markers.The 1000 pairs of SSR makers were selected for screening in the two parents and screened 120 pairs of available polymorphic primers were further screened in 176 F₂populations,finally,40 pairs of polymorphic primers were obtained.The results showed that there were a total of 53available markers in the F₂ population,which were 44 markers successfully used for linkage analysis in total.Finally,3 linkage groups were constructed,the genetic linkage map was 761.97CM,and the average of each marker interval was 17.3CM.The length of Ch01 is 705.84CM,including 34 markers,with an average distance of 20.76CM;the Ch03 is 25.99CM,including 5 markers,with an average of 5.20CM;the total length of ch06 is 30.14CM,with an average distance of 6.09CM.We selected the phenotype data of F₂ and F_2:3 for QTL mapping of branch angle and related traits,including branch angle and related 7 QTLs were mapped to the Chr01linkage group,and the corresponding chromosome was A07.The LOD values of the QTL ranged from 1.74 to 2.65,and the explained phenotypic variation rate ranged from2.18 to 9.73%.Among them,q BAYL-1 has a contribution rate of 6.01%,three QTLs for main inflorescence length are located,and one QTL for primary effective branch height is located in Yangling and Qianxian environments,respectively,and one overlapping QTL between q PHQX-1 and q MILQX-1 is detected.3.BSA for mapping of branch angle Traits.We were constructed four pools by using the parents and 30 plants with extreme branch angles from the F_2:3generation.The SNPs and Indels were select for analysis.The results showed that candidate intervals were identified at A07,A08,C01,C03 and C04,and a candidate interval for the branching angle trait was identified,locus to the3.85CM fragment on the C03 chromosome.Functional annotation was performed on the genes in the candidate interval,and 48 genes were predicted to be related to branching angle formation.