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

Botrytis cinerea, 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 Trichoderma isolates (T1–T7), collected from the rhizosphere of grapevine in Morocco, using a combination of in vitro and in planta 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 in planta 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 Trichoderma & B. cinerea 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.