Microspore culture reveals high fitness of B. napus-like gametes in an interspecific hybrid between Brassica napus and B. oleracea

The strategies of crossing B. napus with parental species play important role in broadening and improving the genetic basis of B. napus by the introgression of genetic resources from parental species. With these strategies, it is easy to select new types of B. napus, but difficult to select new types of B. rapa or B. oleracea by self-pollination. This characteristic may be a consequence of high competition with B. napus gametes. To verify the role of gamete viability in producing new B. napus individuals, the meiotic chromosome behavior of the interspecific hybrid between B. napus (Zhongshuang 9) and B. oleracea (6m08) was studied, and microspore-derived (MD) individuals were analyzed. The highest fitness of the 9:19 (1.10%) pattern was observed with a 5.49-fold higher than theoretical expectation among the six chromosome segregation patterns in the hybrid. A total of 43 MD lines with more than 14 chromosomes were developed from the hybrid, and 8 (18.6%) of them were B. napus-like (n = 19) type gametes, having the potential to broaden the genetic basis of natural B. napus (GD = 0.43 ± 0.04). It is easy to produce B. napus-like gametes with 19 chromosomes, and these gametes showed high fitness and competition in the microspore-derived lines, suggesting it might be easy to select new types of B. napus from the interspecific hybrid between B. napus and B. oleracea.