Bao, J.R., Department of Plant Pathology, Agricultural Research Organization, Volcani Center, P.O. Box 6, Bet Dagan 50250, Israel, Dept. Plant Pathol. and Microbiol., Hebrew University of Jerusalem, Fac. Agric., Food and Environ. Sci., P.O. Box 12, Rehovot 76100, Israel
Katan, J., Dept. Plant Pathol. and Microbiol., Hebrew University of Jerusalem, Fac. Agric., Food and Environ. Sci., P.O. Box 12, Rehovot 76100, Israel
Shabi, E., Department of Plant Pathology, Agricultural Research Organization, Volcani Center, P.O. Box 6, Bet Dagan 50250, Israel
Katan, T., Department of Plant Pathology, Agricultural Research Organization, Volcani Center, P.O. Box 6, Bet Dagan 50250, Israel

Nitrate-nonutilizing (nit) mutants were used to determine vegetative compatibility among 34 isolates of Verticillium dahliae from cotton, potato, olive, eggplant, chrysanthemum and tomato from 12 sites in Israel. Based on the formation of complementary heterokaryons, 33 isolates were assigned to two vegetative- compatibility groups (VCGs): one VCG contained 15 isolates from cotton, eggplant, chrysanthemum and olive; and the other VCG contained 18 isolates from potato, olive and cotton. The status of an additional isolate from tomato, which was compatible with both VCGs, remained unclear. In a limited pathogenicity test with 10 isolates, two (from tomato and eggplant) were pathogenic on tomato, eggplant and cotton; most isolates from cotton were pathogenic on cotton and eggplant only; and one from cotton was non-pathogenic. Fewer isolates were pathogenic on tomato than on cotton or eggplant. The diversity of vegetative compatibility found in our V. dahliae collection is comparable to that found in studies of American populations.