Abstract: Thirty-one strains of Corynespora cassiicola isolated from cucumber，tomatoe and eggplant in Shandong，Liaoning and Beijing，and 10 strains isolated from rubbers in Hainan Province were studied. The pathogenicity of the whole 41 isolates of Corynespora cassiicola to cucumber，tomato and eggplant was investigated by means of spray inoculation at seedling stage. The results showed that the pathogenicity of the isolates originated from different hosts had significant differences. There existed a strong correlation between the origins of hosts and the pathogenicity of the strains. It was proved that the intraspecific strains of Corynespora cassiicola bore a high host specialization. Furthermore，the isolates of Corynespora cassiicola collected from the same host or location showed different pathogenicity as strong，intermediate，or weak. It indicated that there was a distinct phenomenon of pathogenicity differentiation among Corynespora cassiicola strains.

Key words: Corynespora cassiicola, pathogenicity, host specialization