Vegetative Compatibility and Pathogenicity of Verticillium dahliae Kleb. Isolates from Olive in Israel

Fifty-two isolates of Verticillium dahliae from olive trees grown at different locations in Israel were assigned to vegetative compatibility groups (VCGs), using nitrate non-utilizing (Nit) mutants. A higher frequency of nit1/nit3 mutants (95%) was obtained compared with NitM (5%), with 81% of the isolates being assigned to VCG4B and 19% to VCG2A. The pathogenicity of 14 randomly selected isolates (seven of each VCG) was tested on olive twigs (cv. Picual) and tomato. VCG4B and VCG2A isolates were similarly aggressive on olive. However, VCG2A isolates were more aggressive on tomato (line 139) than the VCG4B isolates as indicated by a higher colonization index