Manganese affects grapevine wood degradation by Fomitiporia mediterranea: in vitro evidence

Summary. Grapevine trunk diseases (GTDs) are severe constraints affecting Vitis vinifera (grapevine) cultivation, causing vine decline, yield losses, and major economic impacts. Within the Esca disease complex, the white-rot basidiomycete Fomitiporia mediterranea is frequently associated with wood degradation. Despite its recognized involvement in disease development, the influence of abiotic factors on the wood-degrading activity of this pathogen has not been studied. Effects of manganese (Mn2+) availability on F. mediterranea growth, biomass production, wood degradation, and manganese peroxidase (MnP) activity of this fungus were assessed under controlled laboratory conditions, using increasing manganese concentrations and young (3-year-old) and old (25-year-old) wood from V. vinifera ‘Cabernet Sauvignon’. Manganese availability had a concentration-dependent effects on F. mediterranea. Intermediate Mn2+ concentrations, particularly 80 µM, promoted colony growth, biomass accumulation, and wood mass loss, whereas greater concentrations (320 µM) reduced growth and wood degradation. Qualitative observations showed formation of dark pigmented zones in wood, which became progressively more pronounced as Mn concentrations increased. MnP activities were greatest at intermediate Mn2+ levels, and declined at the greatest concentration, a trend consistent with F. mediterranea growth and wood degradation patterns. These results indicate that Mn2+ availability can modulate F. mediterranea degradative activity and may influence enzymatic processes involved in grapevine wood decay. Future studies should assess micronutrient bioavailability as an abiotic factor for reducing progression of the Esca complex in grapevines.