Pathogenicity Division of Plasmopara viticola in Three Provinces

11 strains of Plasmopara viticola were isolated from materials collected from Hebei,Henan and Shanxi Provinces. Their pathogenicity was investigated by inoculating on 8 selected grape cultivars. Comparing the leaf disc floating method with defoliation method,the latter one was more suitable for determining the pathogenicity of P. viticola. The pathogenicities of the tested strains were divided into 2 categories. The paper had provided a basis for pathogenicity division of P. viticola for other regions. At the same time,it provided a theoretical foundation for scientific control and reasonable layout of grape varieties.