Dissecting A QTL Cluster Of Seed Oil Content On C2 Chromosome By Molecular Markers In Brassica Napus L.

Rapeseed {Brassica napus L.) is an important oil crop worldwide, and seed oil content is the main determinant of its value. So, increasing the seed oil content of rapeseed becomes the main objective of many scientists.There is a segregating population of 202 double haploid lines (designated as TN DH population) and a genetic map in our Lab. This population is derived from a cross between Tapidor, a European winter cultivar of Brassica napus L., and Ningyou7, a Chinese semi-winter cultivar. Tens of QTL related to seed oil content variation with the populaton were identified, and a QTL cluster was detected on the C2 linkage group of the map (designated as qcO.C2). This cluster explained 25% of the phenotypic variation with superior alleles contributed from Tapidor. Based on the resources and information above, we developed near isogenic lines (NILs) for dissecting the QTL cluster with backcrossing, phenotype screening and molecular marker assisted selecting. Because of the limitation of markers on C2 and the QTL region (25 markers and 8 markers, respectively), adding more powerful markers in the QTL region is required for dissecting genetic control of qcO.C2 and gene cloning.Different methods of developing molecular markers were applied for adding more markers on C2 in this study:1. A total of 672 pairs of SRAP primer were screened in three-step procedure with Bulked Segregant Analysis (BSA) strategy. As a result, 11 SRAP markers were located on C2, and 37 SRAP markers were located on another 14 linkage groups. Then these newly developed markers on C2 were sequenced and analysed. Two SRAP markers were transformed into SCAR markers successfully, and these SCAR markers have been involved in marker assiated selection for developing NILs.2. A total of 200 pairs of AFLP primer were screened with the same strategy above. As a result, five AFLP markers were located on C2, and 34 AFLP markers were located on another 13 linkage groups. And then, these new markers on C2 were also done sequence-analysis.3. Base on the sequence of new markers on C2, in silico mapping with Arabidopsis genome sequence was done. We analysed some sequence from B. rapa genome and Tapidor BAC end according to the result of in silico mapping. Then, eight STS markers were newly developed and located on C2, and six STS markers were located on another four linkage groups.In summary, 27 new markers were added onto C2 from this study. The marker density of C2 was increased from lMarker/5cM to lMarker/2.6cM. And then, QTL mapping was practiced for seed oil content variation from 12 experiments again. The number of QTL on C2 was increased, from 13 to 20. After meta-analysis, the location of QTL was concentrated than before, and the QTL confidence interval was also refined. There were three synteny blocks (C5A, C5E and C1E) of Arabidopsis genome identified sequentially along the confident interval of qcO. C2 after in silico mapping analysis, and nine candidate genes related to seed oil formation were discussed.