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 .