Identification of the Chestnut Endophyte Trichoderma nordicum FPYF2509 and the Antifungal Potential of Interaction-Induced Myrtenol Against Fruit Rot

This study aimed to develop biofumigation strategies against chestnut fruit rot caused by Botryosphaeria dothidea. An endophytic strain, FPYF2509, was isolated from Castanea mollissima fruit and identified as Trichoderma nordicum using morphological and phylogenetic (tef1, rpb2) analyses. Antifungal volatile organic compounds (VOCs) were analyzed using headspace solid-phase microextraction and gas chromatography–mass spectrometry during dual-culture interactions with pathogens. The volatiles from the interaction exhibited to inhibit pathogen growth. Particularly an induced myrtenol, demonstrated strongly biofumigation activity in vitro, with a lowest observed effect concentration of 0.02 µL/mL, minimum inhibitory concentration and a minimum fungicidal concentration of 0.2 µL/mL against B. dothidea. In vivo, fumigation with 0.2 µL/mL myrtenol significantly reduced disease incidence from 83.3% to 17.39%, achieving a 79.1% control efficacy. This work presents endophytic T. nordicum FPYF2509 as a promising biocontrol agent and identifies myrtenol, of fungal interaction origin, as a novel and effective mycofumigant for postharvest disease management.