Stability of Colletotrichum truncatum in culture influences mycoherbicide efficacy

Colletotrichum truncatum, a potential mycoherbicide for control of hemp sesbania, formed spontaneous variants on agar medium. The predominant variant produced more spores than the wild type on potato dextrose agar but the wild type produced more spores on Czapek-Dox agar. Spore yield of both types was greatly reduced on Czapek-Dox. In liquid culture, the variant spontaneously arose and gradually displaced the wild type. Although the variant produced more spores in liquid culture, it had reduced virulence. Displacement of wild type strains by similar variants in liquid fermentation may constrain production of this mycoherbicide and should be considered during the preparation of C. truncatum inocula.