Plasmodial formation in the Myxomycete Physarum polycephalum is under heterothallic control by a mating type (mt) locus. In natural isolates only amoebae with different mt alleles are able to cross to form diploid plasmodia. A class of mutants isolated from heterothallic amoebae, together with the variant strain CL, is able to form plasmodia in pure clones, designated as selfing. Non-selfing mutants have been isolated from CL and from other selfing amoebae.
This paper reports the isolation and analysis of 64 non-selfing derivatives (designated Npf−) from seven selfing (Het−) strains. The Npf− mutants could be grouped into eight classes on the basis of their crossing and complementation patterns. The possible significance of these mutants is discussed.