Allelic diversity in a novel gene pool of canola-quality Brassica napus enriched with alleles from B. rapa and B. carinata

Brassica napus is an amphidiploid with genome AACC and is relatively deficient in genetic diversity. The abundant genetic diversity in other A- and C-genome Brassica species is a valuable resource to expand the narrow gene pool of B. napus. Recently the A(r) genomic components from Chinese B. rapa (A(r)A(r)) and C(c) genomic components from Ethiopian mustard B. carinata (BBC(c)C(c)) were introgressed into B. napus through interspecific hybridisation, and the A(r)/C(c) components were enriched through two generations of molecular marker-assisted selection. In this study, the simple sequence repeat (SSR) allelic diversity of 29 of these new-type B. napus lines, 12 from the first generation and 17 from the second generation, was compared with 66 international B. napus varieties from Australia, China and other countries. Hierarchical clustering and two-dimensional multidimensional scaling revealed that second generation lines and a few first generation lines, all selected for high A(r)/C(c) components, formed a unique population that was distantly separated from international B. napus. This novel gene pool had significantly higher richness of private SSR alleles and more alleles per SSR marker than the international B. napus varieties. The new-type B. napus lines showed variation in agronomic traits beyond the canola-quality B. napus parent. Many of the lines had low erucic acid and low glucosinolates in the seed (canola quality), indicating that they could be utilised immediately in canola breeding programs.