Sex ratio in hybrids between Silene alba and Silene dioica: evidence for Y-linked restorers.

Sex ratio in Silene alba is generally female biased, and the bias is influenced by Y-linked alleles that are polymorphic in natural populations. One interpretation of these alleles is that they enhance the production of males in female-biased populations, i.e. they are restorers. Two Silene species, S. alba and S. dioica, and their reciprocal hybrids were used to investigate the inheritance of sex ratio and the relationship between sex ratio and male fertility. Sex ratio was paternally inherited (i.e. Y-linked), but was also strongly influenced by the maternal parent through an interaction with the Y chromosome. These results corroborate previous work on the inheritance of sex ratio within S. alba, and suggest that sex ratio in S. alba and S. dioica has a similar genetic basis. Examination of the maternal by Y chromosome interaction revealed that the Y chromosome of each species produced a more severe female bias in crosses with females of the opposite species. This is consistent with the hypothesis that the alleles expressed in the maternal parent cause the female bias, while the Y-linked alleles tend to restore sex ratio toward equality.