Genes influencing selective fertilization in Neurospora crassa.

The mutual attraction of conidia to protoperithecia of the opposite mating type was studied genetically in crosses where a mixture of conidia from two different strains, one of which was marked by an ascospore color mutant gene tan spore (ts), was applied to protoperithecia. Selective fertilization was measured as the frequency of perithecia fertilized by conidia from one strain in competition with conidia from another strain. Selective fertilization by a given strain varied throughout the range from 10 to 97% according to the strains of protoperithecial parent. The selective fertilization was revealed to be under the control of two or more loci, which appeared to have multiplicative action. No indication of a cytoplasmic effect on selective fertilization was obtained. The strength of the mutual attraction between conidia and protoperithecia decreased as genetic similarity increased.