Dual Evidence of Trichoderma pleuroti Antagonism against Pleurotus pulmonarius: Direct Inhibition and Volatile-Mediated Bioassays with Volatilome Fingerprinting.

Trichoderma is known to cause green mold contamination, which severely threatens Pleurotus pulmonarius cultivation in tropical regions, including Malaysia, and can lead to major yield and economic losses. In this study, the contact-dependent and contactless antagonistic interactions between Trichoderma pleuroti and P. pulmonarius were investigated, and associated morphological changes and volatile profiles were characterized. Dual-culture assays recorded rapid overgrowth of P. pulmonarius by T. pleuroti, leading to growth suppression and mycelial discoloration. Light and scanning electron microscopy demonstrated aggressive mycoparasitism in T. pleuroti, which showed hyphal deformation and specialized structure attachment at the interaction interface. Inverted and tripartite plate methods were used to evaluate volatile-mediated effects. In P. pulmonarius, exposure to T. pleuroti volatiles induced abnormal mycelial thickening and growth inhibition, consistent with a contribution of fungal volatiles to contactless antagonism. Headspace gas chromatography-ion mobility spectrometry revealed distinct volatilome patterns and identified several candidate VOC features associated with T. pleuroti, including 1-octanol, 1-octen-3-ol, 3-octanol, (E)-2-hexenal, (E)-2-heptenal, (E)-2-octenal, acetic acid and butanoic acids. Overall, T. pleuroti exhibited both contact-dependent and contactless antagonistic effects against P. pulmonarius mycelium, involving mycoparasitic interactions and volatile-mediated inhibition. These findings provide insights into the development of green mold disease in Pleurotus cultivation and contribute to a better understanding of fungus-fungus interactions in mushroom production.