ULTRAVIOLET LIGHT-INDUCED HETEROKARYON FORMATION AND PARASEXUALITY INCRYPHONECTRIA-PARASITICA

The effect of ultraviolet-light on heterokaryon formation, vegetative compatibility, and parasexuality in Cryphonectria parasitica was exami ned. Heterokaryons of complementary auxotrophic strains could not be m ade by hyphal anastomosis if the strains belonged to different vegetat ive compatibility groups. Protoplast fusions overcame incompatibility of strains differing in the alleles of a single but not multiple veget ative incompatibility loci. Fusion of protoplasts from ultraviolet lig ht-treated complementary auxotrophs increased heterokaryon formation b y 10(4) to 10(5) using the strains differing in alleles of a single ve getative incompatibility gene but had no detectable effect on strains differing in multiple vegetative incompatibility genes. Vegetative com patibility tests of single conidial isolates resolved from these heter okaryons suggest that diploids had formed followed by the loss of one of the VIC alleles. Presence of both auxotrophic markers in some of th ese single conidial isolates confirms the occurrence of a parasexual c ycle. These experiments demonstrate that ultraviolet-light can enhance heterokaryon formation and parasexuality in C. parasitica. (C) 1995 A cademic Press, Inc.