Interest in in vitro study of entomopathogenic fungi, including Cordyceps species, has been increasing due to their valuable bioactive compounds and biocontrol effects. Among Cordyceps species, in vitro stromata of C militaris has been successfully produced and cultivated for industrial purposes. However, genetic study on in vitro stromata formation of C militaris has not been carried out yet. Here, relationship between mating system and perithecial stromata formation of C militaris is reported. Mating system was determined by observing perithecial stromata formation from mono-ascospore cultures and their pair-wise combinations. Certain combinations of mono-ascospore strains produced perithecial club-shaped stromata, whereas other combinations produced either no stromata or only abnormal non-perithecial stromata. Similarly, monoascospore cultures without combination produced either no stromata or only abnormal nonperithecial stromata. Despite obvious heterothallism, self-fertility was occasionally observed in few strains of C militaris. These observations indicated that C militaris behaves as a bipolar heterothallic fungus and requires two mating compatible strains in order to produce regular clubshaped perithecial stromata, a fundamental requirement for its industrial cultivation.
