Characterization of hybrid seedlings from crosses of Nicotiana stocktonii Brandegee×N. tabacum L. and N. stocktonii×progenitors of N. tabacum

Abstract

Hybrid lethality is one of the sexual barriers preventing wide hybridization. In the genus Nicotiana, hybrid lethality is observed in some interspecific cross combinations. Interspesific hybridization of Nicotiana stocktonii×N. tabacum has not been carried out from the viewpoint of expression of lethality. N. tabacum has an S subgenome derived from N. sylvestris and a T subgenome derived from N. tomentosiformis. In this study, hybrid seedlings from the cross N. stocktonii×N. tabacum, were obtained by ovule culture. The hybrid seedlings were classified as normal seedlings, tumorous types and vitrified plants, and they did not express lethality. Hybrid seedlings from the cross N. stocktonii×N. sylvestris expressed lethality. Moreover, hybrid seedlings from N. stocktonii×N. tomentosiformis also expressed lethality. This suggests that both the S genome of N. sylvestris and the T genome of N. tomentosiformis have factors causing lethality in hybrids with N. stocktonii. However, hybrid seedlings from N. stocktonii×N. tabacum did not express lethal symptoms in this study. We suggested that the factors responsible for lethality in N. tabacum must have been lost or no longer expressed during the process of speciation, probably due to reorganization and modification of the genomes.