We determined DNA fingerprint haplotypes and pathotypes of the rice-blast fungus Magnaporthe grisea collected from 13 areas in China. This DNA fingerprinting analysis, using rep-PCR, of 381 haplotypes (482 isolates) from China indicated that the M. grisea populations cannot be delineated into region-specific groups. Analyses of the number of alleles ( na), Nei's gene diversity, unbiased genetic distance, and Shannon's Information index among 13 populations showed that clusters were not related to the geographic distance between populations with the exception of the Ningxia (NX) and Jilin (JL) cluster. Among northern populations, NX and JL were more similar to one another than to other populations. Pathogen populations consisting of 121 isolates from China were grouped into 53 pathotypes on the basis of disease reaction in differential rice lines. Isolates assayed for pathotypes were detected based on disease reactions. No correlation was observed between fingerprint groups and pathotypes of the pathogen. High frequency of virulence was found on the rice line Shin2 ( Pi-ks and Pi-sh) followed by PiNo.4 ( Pi-ta2 and Pi-sh) and K1 ( Pi-ta), while it was low on Kanto 51 ( Pi-k + ?), K3 ( Pi-kh), and Fujisaka ( Pi-i and Pi-sh). Virulence was rare on Toride 1 ( Pi-zt and Pi-sh). Tetep (Pi-kh + ?) was predicted to be a highly effective, as none of the isolates infected this line. These blast-resistant rice lines can be used in resistance breeding for the effective management of rice blast in the respective regions of China. [ABSTRACT FROM AUTHOR]