Abstract: Eightytwo R. solani strains and 13 standard anastomosis group strains were used in the sequence analysis of 58S rDNAITS (ITS) interval. The differences in sequences of ITS interval among anastomosis group strains were much larger than that among the AG1IA strains. Phylogenetic analysis showed that the differences in sequences of ITS interval could effectively distinguish strains from different anastomosis groups. But when the strains belonging to the same anastomosis group were concerned， the usage of the differences in sequences of ITS interval was quite limited. Haplotype analysis showed that 82 rice strains could be divided into 10 haplotypes．
Haplotype diversity (Hd) of these field isolates was 02087， and the total nucleotide diversity was 000033. H1 was the dominant haplotype， accounting for 878% of all strains， while each of the other nine haplotypes only contained one strain. Neutral test results showed that Tajimas D test value was　-226012 (P<001) and Fu and Lis D test value was -520827 (P<002)， implying that rice sheath blight strains might significantly deviate from neutral equilibrium hypothesis that the R. solani population may be under expansion in the history under strong selection pressure．

Key words: Rhizoctonia solani, rice, internal transcribed spacer, sequence analysis, haplotype