Fungi Associated with Populations of Heterodera Glycines in Two Illinois Soybean Fields

Fungi were isolated from Heterodera glycines cysts collected every 3–4 weeks for three consecutive years in two Illinois soybean fields. Sixty-nine species of fungi were identified, including a number of potential nematode pathogens. Fusarium solani, F. oxysporum, Stagonospora heteroderae, Gliocladium roseum, Paraphoma radicina, Pyrenochaeta terrestris, Exophiala pisciphila and Diheterospora chlamydosporia were the most common species isolated in both fields. Populations of H. glycines and associated fungi were compared in the two fields. One field had a typical, high nematode population level, and the second had an apparently suppressed H. glycines population despite years of continuous cropping with susceptible soybean cultivars. Fusarium solani and S. heteroderae were predominant in the first field, and F. oxysporum and P. radicina were predominant in the field with the suppressed nematode population. The mycota associated with the suppressed nematode population was more diverse and fluctuated less than the mycota associated with the high nematode population.