Abstract:

Pythium species were isolated by using petal and leaf baiting methods from soil samples that collected from some nurseries in Beijing in order to realize their distributions. The results showed that there were 5 isolates similarly in morphology and colony and had some differences with other Pythium species already reported in China. Genomic DNA of these 5 isolates were extracted by the improved CTAB method. Multiple sequence alignment was conducted with the type strain CBS 808.96 in terms of the rDNA-ITS sequences, and the result showed that there was a high similarity (99.26%) between them. All the species of the Pythium group which Pythium nunn was in and some species from other groups were selected to be constructed the phylogenetic tree with the method of neighbor-joining. The tree was rooted using Phytophthora polymorphica as an outgroup. Based on the morphological characteristics and the results of sequence analysis,5 isolates recorded in this article were identified as Pythium nunn. Pythium nunn is a potential biocontrol agent that provides test basis for follow-up studies in biocontrol area.