Phylogenetic Analysis of the Sequences of rDNA Internal Transcribed Spacer (ITS) of Phytophthora sojae

The internal transcribed spacer (ITS) region (ITS1, ITS2 and 5.8S rDNA) of the nuclear ribosomal DNA (nrDNA) was amplified via the PCR method in seventeen different isolates of Phytophthora sojae using the common primers of the ITS of fungi. Around 800 bp-1,000 bp fragments were obtained based on the DL2000 marker and the sequences of the PCR products were tested. Taking isolate USA as outgroup, the phylogenetic tree was constructed by means of maximum parsimony analysis, and the genetic evolution among isolates was analyzed. The results showed that there is a great difference between the base constitution of ITS1 and ITS2 among various isolates. The seventeen isolates are classified into three groups, and the isolates from the same region belong to the same group, which shows the variation in geography.