Notes on some Phytopythium and Pythium species occurring in oak forests in southern Poland

Phytopythium and Pythium species are known to be soil-born oomycete pathogens of forest trees in Europe. Little is known, however, about the presence of these micro-organisms in Polish oak forests. During the period 2007–2009 a comprehensive study of Phytophthora species in soils of oak forests in southern Poland was conducted using baiting technique. In this study, baits were also colonized by oomycete resembling Pythium species. Based on morphological characteristics and the ITS sequences comparisons, 10 species of Phytopythium and Pythium were isolated from the soil-root samples, including three putative new species belonging to the genus of Phytopythium. The most commonly encountered Pythium species was Pythium anandrum. The present study demonstrates for the first time that Phytopythium citrinum and Pythium diclinum can also act as soil-borne organisms in oak forests. In addition, these species were reported for the first time in Poland.