Detection and Host Range Investigation of Phytopythium helicoides and Phytopythium palingenes

Phytopythium species are water molds that have been divided as a separate group of oomycetes about 10 years ago. They are associated with diverse environments worldwide, but the ecological function of most of the species is still under investigation. In the present study, isolation and characterization of Pp. helicoides and Pp. palingenes are described. Both Phytopythium isolates originate from an aquatic environment and were derived from infected leaves. A host range of Pp. helicoides and Pp. palingenes using pathogenicity tests with leaves and cuttings from trees, bushes, perennial and herbaceous plants that belong to 15 different families was studied. Out of 21 tested plants, 18 were susceptible to infection with Pp. helicoides and nine were negatively affected by Pp. palingenes. Pp. helicoides is distinguished by higher aggressiveness and a wider range of potential host species. These results indicate that the impact of pathogenic species from the genus Phytopythium on forests and other natural ecosystems could be much more significant than is currently known.