Genetic diversity of the entomopathogenVerticillium lecanii on the basis of vegetative compatibility

Abstract

Forty-three isolates ofVerticillium lecanii from insects, phytopathogenic fungi and other substrates were tested for vegetative compatibility by observing heterokaryon formation among complementary nitrate-nonutilizing (nit) mutants.nit mutants were isolated from 42/43 strains examined. Twenty-one isolates were self-incompatible, and the remaining 21 isolates were divided into 14 vegetative compatibility groups (VCGs): ten containing only a single strain each, and the remaining four containing two to four isolates each. Members of isolates in each of these VCGs all shared the same IGS haplotype. Further, the isolates within a VCG were correlated with one another in part by fragment patterns of mt-LrDNA, -SrDNA, Bt-2 and H4 region, by PCR-RFLP and -SSCP, but not by dsRNA. Two isolates belonging to VL-J2 have high virulence to aphids, whereas strains from VL-J1 lack this character. These findings indicate that two VCGs (VL-J1 and -J2) may originate from two distinct clonal lineages. Alternatively, high VCG diversity and HSI frequency ofV. lecanii might be associated with an array of distinct lineages. These data not only suggest relationships among DNA polymorphisms, virulence, and VCG, but also demonstrate genetic heterogeneity ofV. lecanii.