Fine Mapping Of Two QTLs For Seed Weight On Chromosome A7 Of Brassica Napus

As one of the three yield-related key factors of oilseed rape (Brassica nupas L), thousand seed weight is positively correlated to yield. Larger seeds represent the higher yield, protein, oil and seed activity. Consequently, thousand seed weight/seed size plays a crucial role in oil rapeseed improvement.In prior research,297 SSR markers was used to conduct a complete linkage map for SJ-DH population, among 9 TSW (Thousand seed weight) QTLs detected, and in which two major QTLs, TSWA7a and TSWA7b explained the overall 27.6-37.9% of the trait variations in total. The performance of the two loci trait was stable in multiple genetic backgrounds. The preliminary work has laid a good foundation for subsequent fine mapping and positional cloning work.The present study is based on earlier work. Molecular marker-assisted recurrent was used to select of the A7 target regions. The two parent lines would be each other’s recurrent parent and donor parent, and to build high generation backcross populations and segregating populations. And SSR markers were used to comparative map between oilseed rape and Arabidopsis (Arabidopsis thaliana) to predict and clone the candidate genes. The main results were as follows:1. To anchor the target regions by molecular markers. Based on the preliminary mapping results of the target regions, A7 chromosome genome sequence information of B.rapa suggest to anchored the two thousand seed weight QTLs in a region of 5.8 Mb and 4.8 Mb of B.rapa genome by eight SSR markers.2. High-generation populations had been built. BC6F1 backcross populations and BC5F2 segregating populations had been built, the segregating population had in total of 12,000 individuals,2,000 individuals for each of the six directions----the unit loci and double locus under two backgrounds.3. Backcross population was used to test the effect of TSWA7a and TSWA7b. The tests showed that each of the two locus of the two major QTLs contribute to the phenotype up to 0.3g to 1.0g, it can increase the yield per plant 1 to 3g, increased by 6.7% to 22.3%.4. Comparative mapping between oilseed rape and Arabidopsis with SSR markers to predict the candidate genes.5. BnTW1 has been cloned, as the candidate gene of TSWA7a. The two allele gene sequences of BnTW1 and the cDNA sequence from the smaller seed parent had been cloned;. A dominant gene-specific-marker had been developed, and the allele gene’s functional domains were analyzed.