Potato cyst nematode-infected soil as a source of egg and cyst parasitic fungi as potential biocontrol agents

Parasitic fungi are an important natural mortality factor of parasitic nematode populations in plants under environmental conditions. Indigenous parasitic fungi are challenging to develop as biological control agents for plant parasitic nematodes, including potato cyst nematode (PCN). Soils that suppress nematode populations are a challenging source of biological agents. This study aimed to explore PCN-infected soil as a source of egg and cyst parasitic fungi. Infected soils associated with healthy plants were compared with soils associated with PCN-infected plants to explore the presence and activity of putative fungal biological control agents. Parasitic fungi in nematode-infected soil were explored, heat treatment was performed to prove the biological ability of parasitic fungi in soil to suppress PCN population, and the biological activity of parasitic fungi was induced using a baiting technique. Results indicated that fungal activity in some PCN-infected areas of soil might suppress PCN population by parasitism of cysts or eggs. Heat treatment of soil eliminated the biological activity of these fungi against PCN cyst population. Baiting soil with PCN cysts promoted the parasitic activity of the fungi in the infected soil. These results indicate that nematode-infected soil is a source of parasitic fungi as candidate biological control agents.