Vegetative compatibility in the entomopathogen Verticillium lecanii

Isolates of Verticillium lecanii. from insects and other substrates, were t ested for vegetative compatibility by observing heterokaryon formation amon g complementary nitrate-nonutilizing (nit) mutants, Among 33 V. lecanii iso lates, 17 were self-incompatible. The 16 sell-compatible isolates were divi ded into 13 vegetative compatibility groups (VCGs). Eleven VCGs were single -member VCGs, and the remaining two included two or three isolates each. Se lf incompatibility occurred more frequently among isolates with abundant ae rial mycelium, whereas most of the isolates with short or reduced aerial my celium were self-compatible. Virulence to larvae of Bemisia tabaci ranged f rom 0 (four isolates) to 83% mortality 4 d after treatment with conidial su spensions. There was no correlation between the capacity of isolates to ana stomose and their virulence to larvae of Bemisia tabaci: highly virulent is olates were found at similar frequencies among self-compatible and self inc ompatible isolates. Those with abundant aerial mycelium were collectively m ore virulent (28.5% mortality) than those with reduced mycelium (10.7% mort ality). Three isolates belong to VCG VL-11 were all highly virulent.