Abstract
SUMMARY: Two alleles of a gene (rac) unlinked to the mating-type locus (mt) have been identified in strains ofPhysarum polycephalumfrom different laboratories. Heterothallic strains differing inmtalleles cross more rapidly if they differ also in theirracalleles. The recovery of hybrid plasmodia from crosses between apogamic (mth) and heterothallic strains is more likely to be achieved if strains of differentracgenotype are used.
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