Primary Dissection For A QTL Cluster Controlling Flowering And Bolting On C6 Chromosome In Brassica Napus L.

Flowering is a symbol of the transition from vegetative to reproductive stage for higher plants; appropriate flowering is significant for avoiding disadvantageous environments and propagation, and acts as an important factor in deciding crop yield. Therefore, flowering time is an important agronomic trait. Flowering of plants is not only regulated by mutiple endogenous genetic factors, but also controlled by complex environmental factors, such as light and temperature. According to the requirement of vernalization or not, rapeseed can be divided into two types, the winter annuals and the spring annuals. Bolting of B.napus comes before flowering. Bolting earlier can lead to earlier flowering in spring conditions, so that the period of duration can be shortened and land utilization rate was rasied. For this reason, research on flowering molecular mechanism of B.napus has not only theoretical significance in studying plant development, but also have great contribution in creating varieties with high and stable yield.DH population named TN DH population was constructed in our lab .The two parents of this population are winter-typed B.napus variety Tapidor and semi-winter typed variety Ningyou7, respectively. Based on this TN DH population, near-isogenic lines (NIL) with Ningyou7 background and Tapidor alleles in C6 target region were constructed. Furthermore, a TN linkage map including 938 markers was constructed by using the software Joinmap4.0. The early flowering DNA bulks and late DNA bulks were constructed separately and screened by 672 SRAP markers. Finally, six polymorphism markers were located in the target region, and one of them was transformed into a STS marker successfully, named as Bog46-2. Based on comparative genomics, primers were designed due to BACs in R7 linkage group of B.rapa, which have homologous sections with the target region. And three SSCP markers were located. After Tapidor BAC end was sequenced and analyzed, the BES homologous to BACs in R7 linkage group of B.rapa were found out, which also shared 80%-95% identity to the chromosome 1 E block of Arabidopsis. By designing primers in the homologous sequences and mapping, two markers were located in the target region. Besides, due to the fact that B.napus is a tetraploid plant, five and other two STS markers were located on the A2 and A7 linkage regions that homologous to C6 target region.The flowering phenotype of BC4F2 population was affected by snowy cold weather in 2007. Only the NIL plants with Tapidor alleles in the whole QTL region were found to flower earlier than Ningyou7 parent. Then the phenotype and genotype of BC5F2 population planted in winter rapeseed environment in 2008 were analyzed, and we find that markers HG-AP1C6a, BOM09, BOH88 and HS-WA3 have no effect on early flowering as well as the marker CNU053a located on the left side of QTL region. HG-FT-C6a and HG-FT-C6b are two flowering functional molecular markers which have different effects on flowering. HG-FT-C6a and HG-FT-C6b markers with Tapidor parent homozygous alles have more effect than with heterozygous alleles. Otherwise Bog46-2 also has effect on early flowering when NIL plants carry Tapidor parent alles in this locus.