Taxonomy of Verticillium Species Causing Wilt of Horticultural Crops in Quebec

Twenty-three cultures of Verticillium were isolated from 10 species of horticultural plants in Quebec. On the basis of morphological and physiological characters in culture the isolates were grouped into three species: V. albo-atrum R. and B., V. dahliae Kleb., and V. nigrescens Pethybr. These species must be distinguished to eliminate the current confusion on host specialization in Verticillium and the influence of environment on Verticillium wilt.