Abstract:The damage of defoliating Verticillium wilt to cotton production has been getting more serious in recent years. In order to make clear of the differentiation about defoliating Verticillium wilt strains, the cultural characteristics and pathogenicity of 30 defoliating strains from 10 main cotton-producing provinces (or regions) were analyzed using specific molecular markers in the current study. The results showed that the colonies of most defoliating V.dahliae stains were belonged to sclerotium type and the microsclerotium exhibited radial or concentric wheel pattern. There were 63.3% strains with dense hyphae and the rest 26.7% strains with sparse hyphae. The spore production quantity ranged from 3.7×107-18.8×107 spore/mL among the defoliating strains. The pathogenicity of strains showed significant differences, with 71.9% strong virulent strains and 25.0% middle virulence. The results indicated that there were differences in spore production quantity and pathogenicity of the defoliating V.dahliae strains among cotton producing provinces.