An Asymptomatic Sweetpotato-Associated Trichoderma atroviride Isolate Exhibits Pathogenic Behavior Under Postharvest Wound Conditions

Trichoderma atroviride is widely recognized as a beneficial fungus and biological control agent. In this study, a T. atroviride isolate recovered from internal tissue of a symptomless sweetpotato (Ipomoea batatas L.) storage root was evaluated by wound inoculation in two independent experiments. Following 14 days of incubation under warm, moist conditions, T. atroviride consistently induced necrotic tissue around inoculation sites, whereas no visible necrosis was developed at PDA-only wound-control sites. Five out of six inoculated storage roots developed localized lesions of approximately 4.9 mm in radius, while one root developed a substantially larger lesion of approximately 44 mm in radius. T. atroviride was subsequently reisolated from symptomatic tissue and confirmed by morphology and molecular analysis, fulfilling Koch’s postulates under the experimental conditions. These findings demonstrate that this T. atroviride isolate occurring asymptomatically within sweetpotato tissue can exhibit opportunistic pathogenic behavior when storage roots are wounded and maintained under conducive postharvest conditions. This report demonstrated the potential pathogenic behavior of a T. atroviride isolate, and highlights the importance of considering specific isolate behavior when utilizing T. atroviride as biocontrol agent.