Mapping Of The Multilocular Gene Bjln2 In Brassica Juncea

Rape is the most important oil crop inChina. Raising the output of rapeseed is a effective way to ensure the oil supply security of China, and the excellent germplasm resource’s development is an important way to increase the rapeseed output. The carpel numbers are related to production. Multilocular plants per yield is significantly higher than the bilocular plants in the same genetic background. Duoshi, a Brassica juncea landrace originating from the Qinghai-Tibetan plateau, have 3-4 silique locules. Predecessors’ research have shown that the multilocular character of Duoshi were controlled by two recessive genes(Bjln1 and Bjln2), and the Bjln1 gene have been mapped in a region of 208 kb in A7 linkage. On this basis, we hybrided the Duoshi with Tayou2(a bilocular material) to produced F1 and then backcross with multilocular to build BC1. The bilocular plants in BC1 continuous backcross with multilocular to build the BC4 separation group(NIL2) of Bjln2. We tried to map the Bjln2 gene with the AFLP and BSA as well as explore the relationship between Bjln1 and Bjln2. The results of this study are as follows:1. The allelism analysis: The allelism analysis between NIL1(the BC4 separation group for mapping the Bjln1 gene) and NIL2 is to indicated that the Bjln2 gene was not allelic to Bjln1 gene. We hybrided the bilocular plants in NIL1 and NIL2 to produced F1, and then backcrossed the bilocular F1 with multilocular to build BC1. The bilocular plants in F1 continuous self-cross to build the BC1. After assaying the segregation ratio of bilocular plants and multilocular plants in the population of BC1 and F2, BC1 population both have the 1:1 and 3:1 separation ratio; meanwhile, F2 population both have the 3:1 and 15:1 separation ratio, which can explain that the Bjln2 gene was not allelic to Bjln1 gene, the genotype of bilocular plants and multilocular plants in NIL2 were Bjln1Bjln1BjLn2Bjln2 and Bjln1Bjln1Bjln2Bjln2 respectively.2. Marker screening: We builted the NIL2 for mapping the multilocular gene Bjln2. Combining the AFLP and BSA method with the comparing genomics to screen markers linked with Bjln2, we filtrated 17 AFLP markers, an IP marker, a SSR marker and a SCAR marker, in total of 20 markers.3. Construction of linkage map: A linkage map for multilocular gene Bjln2 were constructed, these markers distributed on both sides of Bjln2. The most closest markers on both sides were AL13, N1 and AL15, AL16, At90, with genetic distance of 3.1 cM and 0.7 cM, respectively. Marker A1 was co-separated with Bjln2.4. Gene mapping: After sequencing about the 17 AFLP markers, we inferred that Bjln2 was locaked in B genome. Combining with the rest of the three markers information, we hypothesized that multilocular genes Bjln2 may be located in B7 chromosome.