Hybrid lethality caused by two complementary dominant genes in cabbage (Brassica oleracea L.)

Hybrid lethality, a type of postzygotic reproductive barrier, is important for species. Discovering novel hybrid lethality cases and analyzing corresponding causal genes may provide new insights into the establishment and maintenance of reproductive isolation. In this study, we observed the hybrid lethality phenomena in a cross between two cabbage inbred lines, 09-211 and 09-222. Genetic analysis revealed that the hybrid lethality was controlled by two complementary dominant genes, BolC.HL1.a and BolC.HL2.a, from 09-211 and 09-222, respectively. Further analysis indicated that the two genes conform to the Bateson-Dobzhansky-Muller model. Fine mapping of hybrid lethal genes revealed that BolC.HL1.a was located on the C01 chromosome by Indels HL132 and HL134, with a genetic distance of 0.2 and 0.1 cM, respectively. The interval distance between the two markers was 101 kb. BolC.HL2.a was fine-mapped on the C04 chromosome by HL235 and HL234 at a distance of 0.3 and 0.3 cM, respectively. The physical distance was 70 kb. These findings lay the foundation for cloning the hybrid lethality genes in the future and contribute to our understanding of the molecular and evolutionary mechanisms of hybrid lethality in Brassica oleracea.