Creating And Evaluating Two Intermediate Populations Towards A Gene Pool Of New Type Brassica Napus

Brassica rapa and B. carinata are two natural gene pools of A^r and C^c subgenomes, which can be used to enhance heterosis potential in B. napus. The objective of this study is to create two gene pools of rapeseed, carrying considerable genetic variation in A^r and C^c with the following accomplishments.276 allohexaploid lines were developed by crossing 100 accessions of B. carinata with 29 accessions of B. rapa randomly. The hexaploids were pollinated with 8 lines of partial new-typed B. napus, which carded 80% of A^r/C^c subgenomic components developed by our lab previously. And 620 individuals of 198 combinations were harvested from 340 pentaploid combinations to construct the C^c Polymorphic F₁ population (C^cP-F₁ population).Similarly, another A^r Polymorphic population (A^rP population) with larger variation in A^r genome was constructed by crossing 214 accessions of B. rapa with 7 of B. carinata. The A^rP-F₁ population contain 919 individuals of 246 pentaploid combination. Some agronomic traits in A^rP-F₁ population were observed. And another 265 allohexaploid lines were divided.A specific primer to detect B genome was employed to screen individuals of C^cP-F₂ population. And 32.5% of the individuals from C^cP-F₂ population lost B genome. Moreover, the observation of chromosome number among 50 individuals without B genome showed that 56% of the individuals have 38 chromosomes. So it was believed that about 18.2% of the individuals in the C^cP-F₂ population were new type B. napus which contain 38 chromosomes without B genome.53 individuals without B genome from the C^cP-F₂ population were employed to analysis population structure together with 35 accessions of natural B. napus and 8 accessions of the other 5 species of Brassica. 146 polymorphism bands were observed with 37 pair of SSR primers. The new type B. napus have higher heterozygosity than natural B. napus. The result of analysis of duster and PCA showed that new-typed B. napus exhibited a rather high diversity. The average genetic distance in new type B. napus is 0.355 which is higher than Chinese and the other country's B. napus. It illuminated that introgressing the gene resource from B. rapa and B. carinata made the genetic base wider.