Abstract
Key messageOgura CMS fertility-restored materials, with 18 chromosomes, normal seed setting, stable fertility and closer genetic background to the parent Chinese kale, were successfully developed in B. oleracea via a triploid strategy for the first time.Ogura cytoplasmic male sterility (CMS) is the most widely used sterile type in seed production for commercial hybrids of Brassica oleracea vegetables. However, the natural Ogura CMS restorer line has not been found in B. oleracea crops. In this study, the triploid strategy was used with the aim to create euploid B. oleracea progenies with the Rfo gene. The allotriploid AAC hybrid YL2 was used as a male parent to backcross with Ogura CMS Chinese kale. After successive backcrosses, the BC2Rfo-positive individual 16CMSF2-11 and its BC3 progenies, with 18 chromosomes, were developed, which were morphologically identical to the parent Chinese kale. Compared with F1 and BC1 plants, it showed stable fertility performance, and regular meiosis behavior and could produce seeds normally under natural pollination. The genomic composition analysis of Rfo-positive progenies by using molecular markers showed that more than 87% of the C-genome components of BC3Rfo-progenies recovered to the parent Chinese kale, while most or all of the An-genome segments were lost in 16CMSF2-11 and its progenies. The results suggested that the genetic background of Rfo-positive individuals was closer to that of the parent Chinese kale along with backcrossing. Hereof, the Ogura CMS fertility-restored materials of Chinese kale were successfully created via triploid strategy for the first time, providing a bridge for utilizing the Ogura CMS B. oleracea germplasm in the future. Moreover, our study indicates that the triploid strategy is effective for transferring genes from B. napus into B. oleracea.
Highlights
Brassica oleracea is a typical cross-pollination species, and its F1 hybrids exhibit strong heterosis, such as the high yield, better quality, increased uniformity, wide adaptability and resistance to biotic stresses in single cross-hybrids of cabbage, cauliflower and broccoli (Fang et al 1983; Pearson 1983; Kucera et al 2006; Singh et al 2009, 2019; Dey et al 2014)
In cytoplasmic male sterility (CMS) system, the naturally occurring CMS resources are absent in B. oleracea, and most of the CMS types used in B. oleracea were transferred from radish, Brassica napus and other related cruciferous species through distant hybridization (Thompson 1972; Pearson 1972; Yarrow et al 1990; Bannerot et al 1974; Shu et al 2016)
On the other hand, the creation of restorer line might challenge the protection of varieties with this cytoplasm, because some breeders only used Ogura CMS to protect the varieties instead of the plant variety protection (PVP) system
Summary
Brassica oleracea is a typical cross-pollination species, and its F1 hybrids exhibit strong heterosis, such as the high yield, better quality, increased uniformity, wide adaptability and resistance to biotic stresses in single cross-hybrids of cabbage, cauliflower and broccoli (Fang et al 1983; Pearson 1983; Kucera et al 2006; Singh et al 2009, 2019; Dey et al 2014). The male-sterile (MS) breeding system is a widely used, effective method in the production of commercial hybrids of B. oleracea vegetables (Fang et al 2004; Yamagishi and Bhat 2014). Owing to its excellent sterile characteristics, through efforts over several generations, Ogura CMS has been successfully transferred to B. oleracea by distant hybridization and protoplast fusion (Bannerot et al 1974; Walters et al 1992; Dey et al 2011). Ogura CMS is the most widely used CMS type in hybrid seed production for B. oleracea vegetables (Wang et al 2012; Dey et al 2013; Singh et al 2019)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
