Diversity of aquatic Pythium and Phytopythium spp. from rivers and a pond of Gifu city, Japan

Pythiaceous fungi have variety of occurrences in different environments. If these fungi are present in water intended to irrigate crops, they pose high risk as pathogens. Pythium adhaerens, P. aquatile, P. diclinum, P. dissotocum, P. pachycaule and P. torulosum, in addition to asexual isolates of P. dissotocum (Pythium “group F”) and Phytopythium helicoides (the former, Pythium “group P”) were isolated from 5 rivers and a pond in Gifu, Japan, and their diversity were studied. All of the isolated species have been previously recorded from aquatic habitats except for P. pachycaule. Sequencing of the internal transcribed spacer regions of ribosomal DNA (rDNA-ITS) including the 5.8SrDNA of these fungi confirmed primary identification based on morphological characteristics. This study proves the dense presence of different species of these Pythiaceous fungi, based on the latest modern identification methods, through which a new genus of Pythium was recorded and divided into two species. The aim of this study was to study the biological diversity of Pythium, which is pathologically important for many crop plants that are irrigated with water from these five rivers and the pond in Gifu, Japan.