SSR Genetic Map Construction And QTL Mapping For Swelling Traits Of Tumor-like Stems In Tuber Mustard (Brassica Juncea)

Tuber mustard (Brassica juncea (L.) Czern. et Coss. var. tumida Tsen et Lee) is one of the important vegetables which swollen stems are used as the main products in mustard varieties in the Cruciferae family. Most of the previous studies focused on the controlling of cell cycle-related genes and environment effects, however, the inheritance of the trait especially the improvement breeding by molecular marker-assisted selection were rare. In this study, we developed a number of SSR primers using the EST sequences from the leaf transcriptome of tuber mustard; a linkage map was constructed with SSR markers using a F2segregation population derived from the two mustard parents, of which, one is stem swelling and the other one is not; the QTL analysis of stem swelling traits were also investigated. The main results were as follows:(1) Both the potential SSR markers detection and the primers design were completed using the SSRLocator I vs.1.8777SSRs were obtained from the EST sequences from the leaf transcriptome of tuber mustard, among which6127pairs of primers were designed. All the primers had a uniform naming (BjSSR0001-B]SSR6127), and were proved to be high-transferable.(2) A linkage map was constructed with116SSR markers using a F2segregation population derived from the two mustard parents, of which, one is stem swelling and the other one is not. It was consisted of17linkage groups covering2061.0cM with an average interval of17.92cM.(3) CIM (Composite interval mapping) mapping methods were applied in studying the quantitative trait loci (QTL) controlling the traits of rumor-like stems swelling in tuber mustard.4QTL loci controlling stem weight were detected,2of them located on the LG3and the others located on the LG13. All the4loci explained high variance of trait ranging from26.46%to28.18%, and their additive effects were all below zero. The QTL loci controlling stem diameter explaining the genetic variation of6.54%located on the longest LG (LG1), and possessed a negative additive effect. The shortest distance between QTL loci and nearest molecular marker was0.99cM, between SD (QTL loci) and BjSSR1811b (marker). None putative QTLs for stem length were detected in the linkage map.