Abstract
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.
Highlights
Brassica oleracea is an important vegetable crop and is genetically diverse, having various subspecies, such as cabbage, cauliflower, broccoli, kale and wild-type, and having many known useful traits, such as its strong resistance against Sclerotinia incorporated from wild subspecies of B. incana [1, 2]
Despite the high frequency of chromosome segregations of 13:15 (36.81%), 12:16 (30.77%) and 14:14 (15.93%) patterns were observed in 182 pollen mother cells (PMCs) at anaphase I (AI), the fitness of the 9:19 (1.10%) pattern was the highest among the 6 patterns observed with a 5.49-fold higher fitness than the theoretical expectation (Fig 2D and 2E)
Meiotic behavior of Brassica interspecific hybrid revealed by microspore culture
Summary
Brassica oleracea is an important vegetable crop and is genetically diverse, having various subspecies, such as cabbage, cauliflower, broccoli, kale and wild-type, and having many known useful traits, such as its strong resistance against Sclerotinia incorporated from wild subspecies of B. incana [1, 2]. B. napus is an important oilseed crop in the world, originating from a natural interspecific hybridization between B. rapa and B. oleracea ~6000 years ago [3, 4]. This crop’s genetic basis was narrower than the parental species due to its short history and domestication through modern breeding methods [5]. Introgression of genetic resources from parental species into B. napus is necessary to broaden and improve its genetic basis [6,7,8,9].
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