Abstract: During 1985-1987,forty-four wheat materials belonging to commercial culti-vars,wheat selections in regional test and s’ources of resistance have been inoculated respectively in greenhouse with 81 isolates of Erysiphe graminis f.sp.tritici coll-ected from different regions in Henan Province.The results showed that the virulence frequency of these isolates on commercial cultivars was higher than 76.55%,the vir-ulence frequency of these isolates on Huapei 28 and Zhou 80-48 belonging to regional test was 6.25% and 8.75% respectively.Pathogenicity association was also analysed.The results of interaction between varieties carrying resistant gene and mildew popula-tion showed similar structure of mildew population in three regiones in Henan Province.Virulent genes V1,V3b,V3c,V5 and V9 have high frequencies(66.67-82.76%),while genes V2,V2 x,V4 and V8 have lowor frequencies(7.06-13.38%).Some questions such as the use of resistent sources in disease-resistance breeding were disscussed.

Key words: Wheat powdery mildew, Viruknee frequency, Pathogenicity association, Virulent gene