GENETIC CONTROL OF RECOMBINATION AND INCOMPATIBILITY SYSTEM IN SCHIZOPHYLLUM COMMUNE

Crossing - over between the a and B loci constituting the A incompatibility factor, gives rise to 2 new specificities which are compatible with both parental A''s and with each other. The frequency of monokaryotic mycelia carrying recombinant A factors is under genotypic control in a multiple crosses program (6 x 6), selection for high and low recombination frequencies (2 generations), and crosses between the selection lines. The data are compatible with a gene-sys-tem consisting of the postulated locus rec which has a major effect on recombination and which is linked to the A factor, and several minor effects by other loci. The apparent dominance of low frequency of recombination of high frequently can be related to the breeding behavior of S. commune. Thus close linkage between a and B permits a high number of A specificities to be maintained in a population as well as high out-breeding potential, while the inbreeding potential (i. e. dikaryotic combinations between monokaryons originating from a single fruit body) is kept low and near its minimum.