[Competition in Antirrhinum majus L].

In Antirrhinum majus selection in the haplophase is investigated, using the segregation in the backcrossprogeny of heterozygotes cae/+(cae)(color of petal-spot).An attempt was made to determine whether the competition depends on gene-action of the locus caeca itself or on a gametophytic gene located in the same chromosome. Three types of progenies can be distinguished: Normal mendelian segregation, or statistically significant deviations with a surplus of "yellow spot" or a surplus of "light, nearly colorless spot" respectively. The hypothesis of an action of the locus cae in the haplophase can be rejected on the basis of these data.The location of a gametophytic gene in the gram-chromosome is assumed. The allele ga (+) comes from the line fim del cae, the allele ga (-)from the standard line S 50. Gametes with the allele ga (+)have a greater chance for fertilization than gametes with ga (-). The competition is found in the progeny of pollen and of egg cells. Two explanations are possible: one gene, which acts in the haplophase irrespective of the sex, or two closely coupled loci, which act in a similar way in the haplophase of each sex respectively. The locus ga is located either between cae and del or distal from cae.