Vegetative compatibility and pathogenecity of Verticillium dahliae kleb. isolates from olive in Iran.

Verticillium wilt caused by Verticillium dahliae is a serious problem of olive trees leading to significant reduction in yield. Verticillium wilt of olive trees was first recorded in Iran 1996 and confirm as due to Verticillium dahliae Kleb. 101 isolates of V. dahliae from olive trees at deferent locations in north provinces of Iran were assigned to vegetative compatibility groups (VCGS), using nitrate non-utilizing (Nit) mutants. A higher frequency of nit 1/nit 3 mutants (93%) was obtained compared with NitM (7%) with 10% of the isolates being assigned to VCG1 and 51% VCG4B and 19% VCG2A. 20% of isolates could not be classified in standard isolates. The pathogenecity of 15 randomly selected isolates (5 of each VCG) was tested on olive seedling (cv. Zard) and eggplant. The VCGs isolates were similarly aggressive on olive. However, VCG1 isolates were more aggressive on eggplant cv. Local than the VCG2A and VCG4B isolates as indicated by a higher colonization index. The pathogenecity tests of the pathogen on test plants (cotton cv. 'sahel', eggplant cv. 'local' and tomato cv. 'ps') show all isolates category in 2 pathogenecity groups defoliate and non-defoliate (with severe and mild subgroups). The morphology of V. dahliae isolates on C'zapeck's agar and water agar medium were different especially for microsclerotia appearance time in culture and their morphology.