In order to determine the pathogenicity of Magnaporthe grisea from Harbin and Jixi cities and simplify the differential system,24 monogenic rice lines were used as differential system to divide the pathogenic types and cluster analyses. The results showed that,by using the monogenic rice lines system,M. grisea from Harbin City could be divided into 34,12 and 27 pathogenic types during 2006—2008,with a similarity coefficient of 0. 32- 1. 00,0- 1. 00 and 0. 20- 1. 00,respectively,and the resistance frequency ...