Microscopic fungi on Nymphaeaceae plants of the Lake Płociczno in Drawa National Park (NW Poland)

The aim of this study was to determine the occurrence of micromycetes associated with disease symptoms on the leaves and flowers of three plant species, Nymphaea alba (NA), Nymphaea candida (NC), and Nuphar lutea (NL), forming nympheid phytocoenoses on Lake Płociczno in Drawa National Park during the years 2009 to 2012. From all collected plant specimens, an overall number of 38 distinct taxa of fungi and chromistan fungal analogues was isolated. The largest diversity of taxa was found on NL (37 taxa), the lowest was on NC (4 taxa), and NA contained 12 taxa. Each year, anamorphic forms of Ascomycota were dominant in the taxonomic structure. For the first time in Poland, Septoria nupharis (NA, NL, NC) and Colletotrichum nymphaeae (NL, NC) were found on their spotted leaves. For both of the mentioned pathogens, Nymphaea candida is a new host plant in Poland. Botrytis cinerea, Elongisporangium undulatum (= Pythium undulatum), Epicoccum nigrum, Fusarium incarnatum (= F. semitectum), and Gibberella avenacea (= Fusarium avenaceum) were found each year in the studied phytocoenoses. The confirmation of NA and NL flower infections by Botrytis cinerea, which leads to gangrene, is an important aspect of the gray mold epidemiology. Until now, the occurrence of smut fungi on nympheids in Drawa National Park was not observed. The taxonomic structure and the predomination of asexual stages of fungi, as well as the similarity coefficients, suggest that the seasonal decomposition of nympheids run naturally and contribute to maintaining the stability of the lake ecosystem.