Parasitism of secondary-stage juvenile of Heterodera glycines and four larva stages of Caenorhabditis elegans by Hirsutella spp.

The fungi Hirsutella rhossiliensis and Hirsutella minnesotensis generally parasitize only plant-parasitic nematodes in nature but parasitize the bacterivorous nematode Caenorhabditis elegans on agar plates. To establish a model system for studying the interaction between fungi and nematodes, we compared the parasitism of the first- to fourth-stage larvae (L1-L4) of C. elegans and second-stage juvenile (J2) of Heterodera glycines by twenty isolates of Hirsutella spp. Although parasitism differed substantially among isolates, both H. minnesotensis and H. rhossiliensis parasitized a higher percentage of H. glycines J2s than of C. elegans larvae. Parasitism of C. elegans L1s was correlated with parasitism of H. glycines J2s. Parasitism of C. elegans by H. rhossiliensis and H. minnesotensis was negatively correlated with larva size and motility, i.e., parasitism was higher for the younger stages. The C. elegans L1 is recommended for studying parasitism of nematodes by H. rhossiliensis and H. minnesotensis.