American Naturalist. 69: 282-283 (1935)
GAMETIC ELIMINATION IN CROSSES BETWEEN SELF-STERILE SPECIES
EDGAR ANDERSON ARNOLD ARBORETUM
HARVARD UNIVERSITY

SINCE the demonstration by East and Mangeldorf (1925) of self-sterility brought about through gametie elimination, similar systems have been reported in numerous genera of the flowering plants. While genetically it is not the only device by which self- and cross-sterility is regulated, it is apparently among the commonest. In crosses between such self-sterile species the gametic elimination might theoretically have perceptible morphological consequences through linkage between the self-sterility allelomorphs and genes affecting size, shape, color, etc. One of the most interesting cases would be provided by a cross between two diploid self-sterile species. The possible genetic set-up in such an experiment is as follows:

In a cross between two self-sterile diploid species we may diagram the self-sterility allelomorphs of the first species as S1S2 and those of the second as s1s2. It will further simplify, the discussion if we refer to the first species as "major" and to the second as "minor." In the F1 there should be four intrasterile, inter-fertile classes of equal size, S1s1, S1s2, S2s1, S2s2. There are six possible combinations between these four classes, as follows:

S1s1 x S1s2 gametic elimination of S1 from major
S1s1 x S2s1 gametic elimination of s1 from minor
S1s1 x S2s2 complete recombination
S1s2 x S2s2 gametic elimination of s2 from minor
S2s1 x S1s2 gametic elimination of S2 from major
S1s2 x S2s1 complete recombination

As regards the self-sterility locus, there are therefore three types of F2's, those in which there is complete recombination, those in which there is elimination of a gene from major, and those in which there is elimination of a gene from minor. The elimination would apply not only to the self-sterility locus but to linked neighboring loci, some of which would certainly affect visible characters, such as size, shape and color. If the two species were at all distinct morphologically one should be able to detect at least a difference between the averages of the three F2's; one intermediate, one closer to major and one closer to minor. It is to be hoped that some one may have the material which will make it possible to test the matter experimentally.

LITERATURE CITED

East, E. M., and A. J. Mangelsdorf. (1925) A new interpretation of the hereditary behavior of self-sterile plants. Proc. Nat. Acad. Sci., 11: 166-171.