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.