Inter-Isolate Heterokaryosis in Thanatephorus Cucumeris I. Between Isolates of Different Pathogenicity

Abstract

Evidence is presented for heterokaryosis occurring between two mutants derived from different pathogenic strains of T. cucumeris from anastomosis group 2. The evidence relates both to the heterokaryon formed and to the recovery in its progeny of a number of markers from the original mutants. Among the progeny were some strains of different pathogenicity from their parents. Synthesis of such a heterokaryon was difficult compared with that between isolates of similar patho-genicity. This would suggest that, in nature, inbreeding of pathogenic strains more commonly operates than outbreeding, resulting in biological isolation of specific pathogenic types. Nevertheless outbreeding, though rare, could be one means whereby new pathogenic strains arise.