STUDIES ON SELF-STERILITY VII. HEREDITY AND SELECTIVE POLLEN-TUBE GROWTH

Abstract

1. In the populations of Nicotiana used in these studies the behavior and inheritance of self-sterility and of its corollary, cross-sterility, are shown to be determined by threea llelomorphic sterility factorsS I,S Za nd SS. 2. The action of these sterility factors is such that the growth of pollen tubes carrying a given factor is inhibited in the styles of plants carrying that factor. 3. As a result reciprocal crosses between plants having one of the sterility factors in common give unlike progenies, and the sterility group tp which the female parent belongs is always absent in the progeny. S S z ? X ss3 3 gives equal numbers of groups S S 3 and sZs3, while the reciprocal cross S1S3 Q X SISz 8 gives equal numbers of groups SS2 and sZs3. The other possible combinations give analogous results. 4. Populations produced by selfing in the young bud stage show the expected segregation. Group SlS2 selfed gives groups SS1, SlSz and S82. Group SS3 selfed gives groups SSl, S S 3 and S3S3. Group S83 selfed gives groups S2S2, sZs3 and S3S3. 5. Tests of various crosses between both heterozygous and homozygous plants have given the sterility and fertility reactions expected by hypothesis. 6. One of the allelomorphs (Sa) in the homozygous condition produces characteristic abnormalities in habit of growth. 7. New material now being tested has given evidence of additional sterility factors. Complete tests have been made on only one type. It proves to be a fourth allelomorph, S4, belonging to the same series as those previously described.