ECOLOGICAL AND PHYSIOLOGICAL STUDIES ON PYTHIUM SPP. FROM AQUATIC HABITATS

Abstract

Pythium species are considered to be of aquatic ongm. Studies on aquatic Pythium spp. have been done by several researchers all over the world. In Japan, few investigators have isolated several Pythium species from pond, lake or sea waters. No comprehensive study has, however, been performed in this respect. Literature review indicated that there is no concrete work concerning isolation of Pythium species from pond water in Osaka district. The purpose of this investigation was to obtain information about the aquatic Pythium flora, with special reference to their phytopathogenicity, in Osaka. Taxonomy, seasonality, physiology of reproduction and production of degrading enzymes of these taxa are presented in relation to the environmental conditions. Three ponds connected together with the same water system in Sakai,

Osaka, were selected. These ponds were subjected to pollution from different sources such as sanitation from the adjacent residential area, rubbish materials and factory side products. Factors affecting asexual and sexual reproduction of some Pythium species were studied in relation to the water pollution. Twenty-four months of study in which monthly sampling of pond waters and 14 months of mud soil sampling were performed, followed by measuring of physical and chemical characteristics of each pond. Isolation of Pythium species was carried out using baiting technique as well as a quantitative method in case of P. jluminum Park var. jluminum (P. fluminum). Virulence was compared for Pythium spp. from pond water and bottom soil. Cellulolytic and pectinolytic abilities of pythia isolated from pond waters were also tested. The results obtained could be summarized as follows.