| Brassica napus is one of the main oil crops in our country. High quality seed oil is a good choice for edibility because of the low content of saturated fatty acids. On the other side, the long carbon chain fatty acids components in seed oil is more like the diesel fuel component, thus seed oil can be a suitable material for biodiesel production. So, increasing the seed oil content of rapeseed is always the main objective of many researchs.A doubled haploid population of B. napus named as TN DH population was constructed with the winter-typed variety Tapidor and the semi-winter variety Ningyou7 in our lab. Seed oil content of the population and the two parent lines in the multi-enviroment tests have been used to detect QTL with the linkage map. Hundreds of QTL related to seed oil content were identified, and a QTL cluster was detected on the C2 linkage group named as qcOCC2. Then, we developed the near isogenic lines (NILs) of the QTL cluster through backcross with the negative effect parent Ningyou 7 under phenotype screening and molecular marker assisted selecting. In order to dissect the qcOCC2 and clone the related genes, we need useful selected markers on C2 linkage group, especially in the confidence interval of qcOCC2.Two kinds of molecular markers were used to densify the linkage group C2 in the research:1. A total of 587 FITO primer flanking SSR markers were developed by Federico et al. according to the sequences of Brassica oleracea. In the previous research, we found that there were three synteny blocks (C5A, C5E and C1E) of Arabidopsis genome identified sequentially along the confident interval of qcOCC2 by in silico mapping analysis. Based on this, we picked out 63 FITO primers for our research. In addition,5 ATH and ZAAS markers which located on C2 linkage group in SG DH population were used in the research. Finally,8 markers are anchored on C2 linkage group in TN DH population, and 7 ATH and ZAAS markers are anchored in the region of qcOCC2. 2. We sequenced the Tapidor BAC-end sequence and aligned the Tapidor BAC-end sequences with the genome sequences of Arabidopsis thaliana to pick out the candidate BACs which were highly homologous (80%) with the C1E, C5A or C5E region of Arabidopsis thaliana. Then, the candidate BAC-end sequences were blasted with the BAC sequences of A2 linkage group in Brassica rapa. The Tapidor BAC-end sequences which were highly homologous (80%-95%) with the BACs of A2 linkage group will be picked out. According to these Tapidor BAC-end sequences, we designed 41 primer pairs, named them as BES marker. Finally,6 BES markers were anchored in the region of qcOCC2.We used the 68 markers anchored on C2 linkage group of TN DH genetic map to analysis 142 rapeseed varieties of Brassica napus, and detected the relevance between the seed quality traits, including seed oil content and mainly fatty acid content, and the tested markers in the natural population with the method of Association Analysis. Then, we find the results of Association Analysis were coincident with the previous results of QTL analysis. The markers which significantly associated with the seed quality traits were almost located in the confidence interval of seed quality traits QTL. So, we make a conclusion:1. There is a certain relevance between seed oil content and the tested markers.2. It has the same alleles which are related with seed oil content in TN population and this natural population. This result affirms the authenticity of seed oil content QTL detection in TN DH population.
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