Bipolar heterothallism, a principal mating system of Cordyceps militaris in vitro

초록

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, mono-ascospore cultures without combination produced either no stromata or only abnormal non-perithecial 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 club-shaped perithecial stromata, a fundamental requirement for its industrial cultivation.

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