Biocontrol of Vitis vinifera Gray Mold via a Culture Filtrate of Trichoderma afroharzianum.

Botrytis cinerea is a devastating pathogen in viticulture, causing gray mold, and bunch rot. Under 25°C, 90% relative humidity and 36 h wetness duration, B. cinerea can lead to yield losses ranging from 20% to 50% in grapevines. This study evaluated the antifungal effects of Trichoderma afroharzianum secondary metabolite filtrates (TSMF) against the B. cinerea isolate MBc5. In vitro dual culture assays revealed that 10 T. afroharzianum isolates inhibited the colony growth of B. cinerea by 42%-88%. TSMF were collected after 30 days of incubation in yeast peptone glucose (YPG) medium and incorporated into potato dextrose agar (PDA) at 10% (v/v) for inhibition testing against B. cinerea. The filtrates significantly inhibited B. cinerea colony growth by 72%-92%. Based on these results, three highly effective isolates (Tr28, Tr138, and Tr153) were selected for in vivo assays. Leaves and bunches were inoculated with B. cinerea (1 × 106 conidia mL-1) and treated, 2 h later with TSMF (2 mL each). TSMF of Tr153 significantly reduced disease severity in leaves (52%-78%) and bunches (70.4%) compared to the pathogen control. Gas chromatography-mass spectrometry (GC-MS) analysis identified butyl acetate as the main component, constituting 39.08% of the Tr153 secondary metabolite filtrate. These results demonstrate that TSMF from T. afroharzianum has strong potential as a biological control agent against B. cinerea in grapevines.