Bioactivity and Mechanisms of Botanical Fungicide Magnolol against <i>Trichoderma hamatum</i> as a Novel Pathogen of Sweet Potato

Sweet potato is a vital crop worldwide, but its storage roots are susceptible to infection by numerous fungal pathogens, leading to substantial postharvest losses. In this study, a highly pathogenic fungal strain was isolated from infected sweet potato storage roots. Through morphological and molecular characterization, the strain was identified as <i>Trichoderma hamatum</i>, representing the first report of this species as a sweet potato pathogen. The botanical compound magnolol exhibited a strong antifungal activity against <i>T. hamatum</i>, demonstrating an excellent protective efficacy against the pathogen-induced disease. Electron microscopy analyses indicated that magnolol could effectively disrupt ultrastructure of <i>T. hamatum</i>. Transcriptomic analyses revealed multiple biological pathways modulated by magnolol. In particular, magnolol could damage the cell membrane integrity of <i>T. hamatum</i> and disturb its energy metabolism. These findings provide critical insights for managing postharvest diseases of sweet potato and highlight the potential of magnolol as a natural antifungal agent for food preservation.