棉 花 学 报 Cotton Science 2007，19(4)：291-295
Preliminary Study on Pathogenicity of Verticillium dahliae in Soil Abstract：In order to explicit the pathogenicity of Verticillium dahliae in soil and to provide the theoretical testimony for the aberrance rule of pathogen，in August 2005，the Verticillium dahliae in the disease garden in the Doukou county，Shaanxi province have been identified. The cultural characters of 26 representative strains of V. dahliae on the PDA substrate showed that there were three cultural type：black (sclerotium type)，white (filamentous fungus) and middle. Furthermore，the growth quantity，formation of micro-sclerotium，fabric，color，size and relative amount of melanin for those 26 representative strains of V. dahliae were different. In addition，the determination of pathogenicity in the seedling stage had also showed that difference existed among the 26 representative strains. According to the reaction types on five species cottons with different resistance，all strains can be classed into three pathogenic types：type 1(12 isolates，accounted for 41.6% of the total) was characterize by severe virulence，type 2(nine isolates，accounted for 34.6%) showed mild virulence and type 3(five isolates，accounted for 19.2%)，an intermediate type.
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