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Isolates of Pythium and Phytophthora species were obtained from rhododendron leaves baits during 2005~2006 in a preliminary stream-baiting survey in the forests of Yunnan and Sichuan Province, Southwest China.Using DNA from purified cultures and the Phytophthora genus-specific primers (Yph1F and Yph2R), 14 isolates were screened.Then using the ITS4 and ITS6 primer pairs about 600~660bp fragment of the internal transcribed spacer regions and 5.8S gene of rDNA was amplified and sequenced from these phytophthoras.Sequence analysis by BLASTn query showed that all 14 sequences shared high similarity of 96%~99% with other Phytophthora spp.and Pythium spp.in GenBank.A phylogenetic tree was constructed for these species based on the ITS sequences using the Neighbor Joining method by MEGA4.0 software.In this phylogenetic tree with other reported Phytophthora and Pythium species, 10 isolates were associated with Phytophthora ITS in Clade 2, 6 and 8;the other 4 were associated with Pythiums.Further species analysis based on molecular and comparative morphological as well as pathogenicity studies is underway.