ABSTRACT
Twenty-five isolates of Pythium species were identi6ed and classified on the basis of RFLP(restriction fragment length polymorphism) of ITS(internal transcribed spacer) region in ribosomal DNA. and M-13 PCR markers. Eight restriction endonucleases were used to investigate the genetic relatedness among isolates P. graminicola and P. arrhenomanes as well as P. aphanidermatum and P. delience produced identical band patterns with all restriction endonucleases used and M-13 markers. P. myriotylum and P. catenulatum also formed tight cluster on the basis of RFLP of ribosomal DNA but produced distinct band pattern with M-13 PCR markers. No intraspecitic variations were observed with RFLP of ITS region in ribosomal DNA. Molecular analysis based on M-13 marker demonstrated that each species produced distinct band patterns. Intraspecific variation of P. ultimum and P. torulosum was observed with M-13 markers.