Confirmation Of The Major QTL For Silique Length And Seed Weight On Chromosome A9of Oilseed Rape(Brassica Napus.L.)

Oilseed rape (Brassica napus L.) is an important oil crop in China. One of the most important goal oilseed rape genetics and breeding research is to increase seed yield. Generally, seed yield is determined by three yield components including total siliques number in per area, seeds per silique and seed weight. As the vital organ, siliques not only provide physical protection for seeds, but also are the main photosynthesis organs at late growth stage. Thus it is of great importance to reveal the genetic basis of silique length and seed weight for yield improvement.A major QTL named cqSLA9was previously identified on chromosome A9of B. napus by Yang Pu, which controls silique length and seed weight of Brassica napus L. In this study, we constructed recombinant inbred lines (NSRILs) by crossing NO.2127with short siliques and SI with long siliques. Silique length (SL), seeds per silique (SS) and seed weight (SW) were investigated in two environments for two years, and QTL for the three traits were identified and analyzed. The main results are as follows:1. Genetic analysis for silique trait:Under the environments of2010Wuhan and2012Hezheng, the broad heritabilities of silique length, seeds per silique and seed weight in NSRIL population were95.53%,62.27%and92.15%respectively. The correlation coefficients between SL and SW were0.47and0.59under the two environments, respectively, showing significant positive correlation between the two traits.2. Construction of A9linkage map:Based on the linkage maps constructed previously using the BnaNZDH and SSRIL populations in our lab,13polymorphic SSR markers on chromosome A9were genotyped in147RILs of the NSRIL population. The chi-square test indicated that marker BnEMS300showed segregation distortion to the S1parent, and BrGMS1093showed segregation distortion to the NO.2127parent. The segregation of the other loci followed the expected Mendelian ration of1:1in recombinant inbred lines. The A9linkage map was constructed based on genotype data of the13molecular markers, which covered83.5cM and had an average interval of6.4cM between adjacent loci.3. QTL mapping for silique length and seed weight:QTL analysis was conducted in the NSRIL population in2010Wuhan and2012Hezheng environment. Four QTL for SL and three QTL for SW were identified. We didn’t detect the QTL for SS on A9linkage group. The QTL qSLA9.1a explained as much as39.01%of the SL variation, and the QTL qSLA9.1b explained as much as11.5%of the SL variation. In2010, qSLA9.1a and qSLA9.1b totally explained50.51%of SL variation, and qSLA9.2a and qSLA9.2b totally explained26.79%variation. In addition, qSWA9.2b and qSWA9.1explained19.70%and13.61%of the SW variation, respectively. The joint effect of qSWA9.2a and qSWA9.2b explained as much as39.06%of the SW variation in2012Hezheng.4. Authenticity of the major QTL cqSLA9:The confidence intervals of qSLA9.1b, qSLA9.2b and qSWA9.2b were overlapped. In addition, the marker Na10-B07closely linked to three QTL was common to the marker linked to cqSLA9, an major QTL for silique length and seed weight identified previously. Thus, these results confirmed that the major QTL cqSLA9controlling silique length and seed weight really exists on A9linkage group of Brassica napus and is stable across environment.