Degradative Activity of Five Basidiomycota Strains on Sweet Chestnut Wood

Basidiomycetes can colonize sweet chestnut (Castanea sativa Mill) xylem, causing white or brown rot and losses in wood quality. The aim of this study was to assess the degradative potential of five Basidiomycota strains (Armillaria mellea (Vahl) P. Kumm. (Am), Fistulina hepatica (Shaeff.) With. (Fh), and Laetiporus sulphureus (Bull.) Murrill (Ls), and two strains of Ganoderma resinaceum Boud.) on three chestnut woods differing in chemistry. The woods differed in nitrogen content (0.3%–1.0%), carbon/nitrogen (C/N) ratio (43–150), and phenolic-related traits. In a 39-day laboratory assay, the five fungal strains were inoculated on three chestnut woods and compared for colonization time, extracellular enzymatic activity, and C mineralization. Fungal colonization strongly depended on fungus × wood interaction: L. sulphureus colonized all woods within 6 days, whereas the two G. resinaceum strains required 9–33 days depending on wood type; A. mellea and F. hepatica colonized only selected woods (up to 39 days). Enzymatic screening indicated laccase activity mainly in G. resinaceum (and to a lesser extent A. mellea), while L. sulphureus expressed cellulolytic activity but no laccase. Over 39 days, total C mineralization peaked under G. resinaceum on the two Sicilian woods (up to 270–300 mg CO2–C g−1 dry wood), whereas the Tuscan wood (highest C/N and phenolic content) markedly inhibited most strains; only L. sulphureus increased mineralization in this wood (85 mg CO2–C g−1 dry wood). These findings indicate that wood chemistry, especially C/N ratio and phenolic traits, strongly modulates strain-specific decay patterns. Overall, these results highlight the need for an integrated biological–biochemical approach to evaluate fungal decay potential and to inform both the selection of more durable chestnut woods for wood products and the identification of efficient strains to accelerate lignocellulosic biomass composting.