Hirsutella rhossiliensisis a parasite of juvenile nematodes, effective against a diversity of plant-parasitic nematodes. Its global distribution on various nematode hosts and its genetic variation for several geographic regions have been reported, while the global population genetic structure and factors underlying patterns of genetic variation ofH. rhossiliensisare unclear. In this study, 87H. rhossiliensisstrains from five nematode species (Globoderasp.,Criconemella xenoplax,Rotylenchus robustus,Heterodera schachtii, andHeterodera glycines) in Europe, the United States, and China were investigated by multilocus sequence analyses. A total of 280 variable sites (frequency, 0.6%) at eight loci and six clustering in high accordance with geographic populations or host nematode-associated populations were identified. AlthoughH. rhossiliensisis currently recognized as an asexual fungus, recombination events were frequently detected. In addition, significant genetic isolation by geography and nematode hosts was revealed. Overall, our analyses showed that recombination, geographic isolation, and nematode host adaptation have played significant roles in the evolutionary history ofH. rhossiliensis.
IMPORTANCEH. rhossiliensishas great potential for use as a biocontrol agent to control nematodes in a sustainable manner as an endoparasitic fungus. Therefore, this study has important implications for the use ofH. rhossiliensisas a biocontrol agent and provides interesting insights into the biology of this species.