Disentangling water restriction and under-vine cover crop effects on grapevine defense-related traits associated with botrytis bunch rot susceptibility

The effects of under-vine soil management and water status on grapevine susceptibility to Botrytis bunch rot (BBR) were evaluated in a pot experiment using Vitis vinifera cv. Tannat. Grapevines were subjected to two soil management practices—permanent cover crop (PCC) and manual weeding (MW)—and two irrigation regimes—a 20-day irrigation restriction starting at the pea-size stage or no restriction. Permanent cover crop significantly reduced BBR incidence and intensity, particularly under irrigation restriction . Disease reduction was associated with increased berry skin cuticle thickness and differential antioxidant responses in leaves and berry skin. These findings suggest that PCC reduces BBR through structural and physiological traits beyond its effects on vine water status.