Hai-long Yu, Zhi-yuan Li, Wen-jing Ren, Feng-qing Han, Li-mei Yang, Mu Zhuang, Hong-hao Lv, Yu-mei Liu, Zhi-yuan Fang & Yang-yong Zhang

Theoretical and Applied Genetics October 2020; vol. 133:2825–2837

Key message

Ogura 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.

Abstract

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 BC₂ Rfo-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 BC₃ Rfo-progenies recovered to the parent Chinese kale, while most or all of the A_n-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.

See https://link.springer.com/article/10.1007/s00122-020-03635-8

Figure 3: Morphological characterization (a–c) and fertility performance (d–k) of the BC₁ hybrid 15CMSF-Y1, BC₂ hybrid 16CMSF2-11 and BC₃ hybrid 17CMSF1-1, respectively. Plant morphology of 15CMSF-Y1 (a), 16CMSF2-11 (b) and 17CMSF1-1 (c). d, e Pollen performance of 15CMSF-Y1 during different flowering periods; f–h Pollen performance of 16CMSF2-11 (f), 16CMSF2-58 (g) and 17CMSF1-1 (h); i–k Pollen viability of 15CMSF-Y1 (i), 16CMSF2-11 (j) and 17CMSF1-1 (k)