Phytophthora species living in Japanese ponds and their habitat preferences

Phytophthora species living in Japanese ponds and their habitat preferences 


Kyoko Tsutsui1*, Hayato Masuya2, Ayaka Hieno3, Koji Kageyama3, Izumi Okane1 


1Faculty of Life and Environmental Sciences, University of Tsukuba, 

Tennodai 1-1-1, Tsukuba, Ibaraki, 305-8572, Japan

2Foresty and Forest Products Research Institute, Forest Research and Management Organization,1 Matsunosato, Tsukuba, Ibaraki 305-8687, Japan.

3River Basin Research Center, Gifu University, 1-1 Yanagido, Gifu, 501-1193, Japan


Phytophthora species are pathogenic oomycetes including causal agents of root rot and wilt of trees, some of which cause significant damage in many countries. It has been suggested that some of these Phytophthora species are invasive species and are believed to be present in Asia. However, there have been few studies of Phytophthora species in natural ecosystems and knowledge of their natural habitat is largely lacking. Understanding the environments suitable for their habitat will lead to the prediction of the pathogen risk, infection routes, and control. In this study, water samples were collected from 40 ponds in the Kanto Plain of Japan, and Phytophthora species were isolated by the baiting method. The studied ponds were divided into three groups based on the percentage of forested area in the perimeter of the pond (“forest cover”) to assume a suitable environment for those Phytophthora species. As a result, at least 12 Phytophthora species were found in 35 of the 40 ponds surveyed, including P. cambivora, P. chlamydospora, P. citrophthora, and P. lucustris. Among them, 10 species have not been reported in Japan, except for P. cambivora and P. citrophthora. A positive correlation was found between “forest cover” and the number of Phytophthora species.