QTL Mapping For Plant Architecture Related Traits And Gene Expression Analysis In Sesame (Sesamum Indium L.)

Sesame?Sesamum indium L.,2n=26?is the traditional and special oil crop in China which has both high edible and nutritional value.Sesame has a long history of cultivation.The improvement of sesame yield has encountered a bottleneck,which is ascribed to its big and loose plant architecture mainly.Improving sesame plant architecture is the main breeding target at present and in the future.As leaf type and plant height together shape the plant architecture of sesame,it is of great significance to study these traits and explore the genes or loci underlying the phenotypes.This study performed on a F₈RIL population derived from Zhongzhi 13 and ZMM2289.In combination with QTL-seq and SSR marker mapping,the QTL related to sesame leaf size was mapped.In addition,sesame gibberellin genes related to the development of plant height were also studied in whole genome-wide.The main results are as following:?1?Sesame leaf size related traits:1/3 leaf length?TLL?,1/3 leaf width?TLW?,1/2 leaf length?SLL?,1/2 leaf width?SLW?of the parents and RILs in three environments were investigated by measuring the length and width of leaves in 1/3 and 1/2 of sesame whole plant from bottom to top.It showed TLL,TLW,SLL,SLW varied greatly among the population,and changed in different environments.The variations of the four traits accord with the characteristic of normal distribution,thus the typical quantitative traits.There was a significant positive correlation between these leaf traits from different environments,especially,between TLL and SLL,and TLW and SLW.?2?Using qtl-seq technology and SSR marker genetic mapping,a total of 59 QTLs were mapped in three environments,including 17 QTLs for TLL and 11 QTLs for TLW,15 QTLs for SLL,16 QTLs for SLW.Of these QTL,9 were repeatedly identified across the three environments,and explained 5.59%to 21.05%of the phenotype variation.Six QTL were repeatedly detected in two environments with the phenotype contribution rate varied from 2.50%-6.78%.The other QTL were identified only in a one environment,in which 21 contributed more than 5%of phenotype variation.?3?In the marker interval between ZMM6185 and ZMM3196,about 2.16cM region,there were four QTL for TLL,TLW,SLL,SLW:qTLL9-1?qTLW9-1?qSLL9-1 and qSLW9-1 were repeatedly identified in three environments with average phenotypic contribution rate 13.84%,thus is the major site controlling sesame leaf size.Then the site was mapped to sesame genome and located in a 408Kb sace between 19996854bp and 20404791bp in Chr9.Through gene annotation of the region,22candidate genes related to leaf size were figured out.?4?Total 32 GA related genes were identified in sesame genome which belong to 7 different gene families,and these genes were distributed on all chromosomes except the chromosome 5.These genes include 5 CPS genes,3 KS genes,2 KAO genes,3 KO genes,7 GA20ox genes,9 GA2ox genes and 3GA3ox genes.In various sesame tissues,the 7 GA related gene families displayed quite different expression patterns.Among the different tissues,the GA related genes generally showed higher activity in the seed,lower activity in the leaf,then in the root tip and in the stem tip.Among them,the genes SiGA20ox6 and SiGA3ox1 were highly expressed in the shoot tips.The homologous genes AtGA20ox1and AtGA3ox1 in Arabidopsis thaliana were proved to be able to elongate the internode in Arabidopsis thaliana.Therefore,it is speculated that these two genes may be involved in the regulation of sesame plant height development.