Cytoplasmic sterility in derivatives ofSolanum demissum

Summary

The crossS. demissum xS. tuberosum has been the basis for many programs of breeding for resistance toPhytophthora infestans. The F₁ of this cross and subsequent back-crosses toS. tuberosum are generally non-functional as male parents; uninterrupted back-crossing is therefore obligatory in programs based on this initial cross. Since recessive and incompletely dominant factors are likely to be lost by continuous back-crossing, the male sterility of such hybrids can be a serious disadvantage. The initial crossS. demissum xdiploid species results in similar non-functional males when crossed withS. tuberosum. However, when F₁ hybrids of the reciprocal cross (diploid species xS. demissum) are crossed withS. tuberosum, many of the resultant hybrids are highly functional as males. These hybrids can be selfed, sib crossed and used as male parents in crosses withS. tuberosum. This difference in the behavior of reciprocal crosses indicates that male sterility inS. demissum derivatives is cytoplasmically conditioned.