Unraveling the Multiple Biocontrol Mechanisms of Trichoderma spp. in the Protection of Grapevines Against Botrytis cinerea

<i>Botrytis cinerea</i>, the causal agent of grey mold in grapevine, remains one of the most economically important pathogens in viticulture and a key target for sustainable biocontrol strategies. This study evaluated the antagonistic potential of seven <i>Trichoderma</i> isolates (T1-T7), collected from the rhizosphere of grapevine in Morocco, using a combination of in vitro and <i>in planta</i> assays designed to capture multiple direct and indirect modes of action. The isolates exhibited variable levels of antagonism through competition, volatile organic compounds, extracellular metabolites, and elicitation responses. Preliminary <i>in planta</i> assays on detached grape berries further demonstrated that all selected isolates reduced lesion development, with preventive applications yielding the strongest protection. Overall, the study highlights the complementary and strain-specific mechanisms underlying <i>Trichoderma</i> & <i>B. cinerea</i> interactions and underscores the importance of isolate selection and application timing for the development of effective and environmentally friendly grey mold management strategies. These findings provide a mechanistic basis for the future evaluation of promising isolates under vineyard conditions.