Korolev, N., 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

Isolates of Verticillium nigrescens and V. tricorpus were obtained from potato, cotton, eggplant, weeds and field soil in Israel. Chlorate-resistant nitrate-nonutilizing (nit) mutants were generated from each isolate and used in complementation (heterokaryon) tests. Eleven vegetative-compatibility groups (VCGs) were found among 19 V. nigrescens isolates from nine sites, and nine VCGs among 26 isolates of V. tricorpus from eight sites. Optimal growth temperature was 24-27 °C for V. nigrescens and 24°for V. tricorpus. None of the isolates caused leaf symptoms or stunting in inoculated eggplant and cotton seedlings, while severe symptoms were caused by V. dahliae. Colonization of inoculated seedlings by V. nigrescens and V. tricorpus occurred primarily in roots and hypocotyls, while V. dahliae heavily colonized upper stems as well.