Occurrence of Nematophagous Fungi in Freshwater Samples of Toba Lake, North Sumatra, Indonesia

Root-knot nematodes are important agricultural pests causing serious economical loss to harvestable crops. Biological control using nematophagous fungi is one option to mitigate these infection through mechanism of physical or chemical killing methods. The present study tried to explore a possibility of finding native nematophagous fungal strains in the hope on discovery of novel and potential isolates originating from freshwater region of Toba Lake, North Sumatra, Indonesia. Isolation of nematophagous fungi was based on sprinkle and pour combination method on Chloramphenicol-Water Agar (CWA) incubated for 30 days. Freshwater samples of soil and sediments were collected from 28 sampling sites characterized by different anthropogenic activities as natural, fishery, residential, plantation and tourism area. Daily examination is conducted to obtain a single culture of nematophagous fungi sub-cultured on Potato Dextrose Agar (PDA) medium. Eleven isolates were observed to initiate predatory activities against tested Caenorhabditis elegans based on qualitative screening. The isolates showed either mechanical killing or chemical killing of nematodes during co-inoculation with nematodes. Micromorphological and molecular analysis are currently being conducted to obtain species identity from each isolate.