OPPOSITIONAL ALLELES IN NATURAL POPULATIONS OF TRIFOLIUM REPENS

Abstract

LTHOUGH the multiple oppositional alleles which condition incompati-A bility have been described for a large number of species [review by STOUT (1g38)], their occurrence in natural populations has been reported in only one previous study. He concluded, however, that the sample which was analyzed was too small to indicate the relative frequencies of different alleles in the entire native population. Extensive tests for the number of alleles were made sipilarly in three other species but in none was a natural population used. In Nicotiana With red clover, WILLIAMS (1941) tested two series of plants, in which he found different alleles as follows: 37 out of 40, and 41 out of 48. In a test of two series of unrelated white clover plants (ATWOOD 1g42b), 25 out of 26 and 34 out of 41, respectively, of the alleles proved to be different. With all four species the test for allelism consisted of making all possible combinations (diallel crosses) between plants which had one S factor in common. Incompatible matings indicated that the two unknown alleles being tested were identical, whereas compatible crosses indicated they were different.