Abortion of male and female gametes in the tomato determined by allelic interaction.

NGIOSPERM gametogenesis, particularly on the male side, is highly susA ceptible to disturbance by either environment o r genotype. Exemplary of environmental agents, sodium a,P-dichloroisobutyrate disrupts pollen development, the effect being sufficiently specific and complete to warrant use of this chemical for purposes of emasculation (EATON 1957). Instances of genetic control are commonplace; at least 30 genes are known in Datura stramonium that condition abortion of the microspores to which they segregate (AVERY, SATINA, and RIETSEMA 1959). In the presence of certain other genes, viable pollen grains may develop, but they fare poorly in competition with grains of other genotypes. Whatever the detrimental effect, segregation of linked genes can be distorted, the degree of distortion depending on the intensity of linkage. Genes affecting gametophyte development are often discovered, in fact, as a result of such distortion. Interest in the present case intensified and the material was investigated in detail when it became apparent that it is exceptional in the following three respects: (1) male and female gametes are equally affected; (2) gametes abort only in certain hybrid combinations; and ( 3 ) the abortion factor behaves as if it were not completely penetrant.