| Abstrakt: |
The cross S. demissum x S. tuberosum has been the basis for many programs of breeding for resistance to Phytophthora infestans. The F of this cross and subsequent back-crosses to S. 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 cross S. demissum x diploid species results in similar non-functional males when crossed with S. tuberosum. However, when F hybrids of the reciprocal cross ( diploid species x S. demissum) are crossed with S. 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 with S. tuberosum. This difference in the behavior of reciprocal crosses indicates that male sterility in S. demissum derivatives is cytoplasmically conditioned. [ABSTRACT FROM AUTHOR] |
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