Volatile Organic Compound Profiling Supports the Detection of Heterobasidion annosum Colonization in Scots Pine Wood

Heterobasidion annosum is a destructive root- and butt-rot pathogen of coniferous forests, and its detection before the development of visible disease symptoms remains challenging. In this study, volatile organic compounds (VOCs) in the headspace of H. annosum-colonized Scots pine wood and fungal cultures were characterized by headspace solid-phase microextraction coupled with gas chromatography–mass spectrometry (HS-SPME/GC–MS) and compared with uncolonized pine wood and uninoculated culture medium. A total of 101 VOC signals were detected, and 98 received putative or tentative assignments. The colonized wood profile was the most diverse and comprised 64 signals, compared with 24 in uncolonized wood, 27 in the fungal culture, and 25 in the culture medium. Principal component analysis and hierarchical clustering of centered log-ratio-transformed replicate-level profiles revealed distinct compositional patterns among the four sample types. Global false-discovery-rate-adjusted q-values were below 0.05 for methyl 2-furoate, iso-longifolene, and 2-(2-furanyl)-1-propanol in the exploratory wood-profile contrast; the corresponding values for 2-methylfuran and β-barbatene were 0.0885 and 0.320. The study provides a preliminary multicomponent relative VOC profile for broader experimental and field validation.