Abstract: The knowledge of virulence and variation of pathogen caused of plant disease is very important to breed resistant varieties and distribute resistance genes. Virulence genes and virulence structure of isolates of Phytophthora infestans collected from twenty nine potato production regions under different ecological types in Yunnan during 2000 to 2003 were determined systematically by a whole set of potato differentials. The results showed that all eleven known virulence genes with different frequency from 2.9～97.8% that could overcome all resistance genes were detected in these isolates. Among the virulence genes, the occurrence frequency of vir1、vir3、vir4、vir7、vir9、vir10 and vir11 were all above 86％ and that of vir5 and vir8 were below 5％. All of 136 isolates showed complex virulence structure, among which 28 different virulence types were detected, and 4-11 virulence genes with an average of 7.3 were existent in each virulence type. The virulence types of 1.3.4.7.9.10.11, 1.2.3.4.6.7.9.10.11, 1.3.4.6.7.9.10.11 and 3.4.6.9.10.11 were prevalent ones during 2000 to 2003. High diversity of virulence of P.infestans were revealed in North-east and north-west planting zones and Middle multiple cropping zones. The supervirulence structure 1.2.3.4.5.6.7.8.9.10.11 was detected firstly in Yunnan. All known resistance genes were susceptible in Yunnan and new resistance resources or breeding strategy need be deployed.

Key words: potato, Phytophthora infestans, virulence gene, virulence