Comparative analysis of aspen, hybrid aspen and poplar xylem mycobiomes reveal tissue-specific patterns in fungal diversity

Fungal communities inhabiting the wood of living trees influence host vitality and wood quality yet remain poorly characterized for many economically important tree species. In this study, the mycobiomes of heartwood and sapwood in three Populus lineages ( P. tremula , P. tremula x tremuloides and species and hybrids in Populus sect. Tacamahaca) were characterized using ITS2 metabarcoding. We observed clear, differences between wood types, with heartwood mycobiomes being less diverse than sapwood communities. Heartwood samples were enriched in fungi belonging to class Leotiomycetes , particularly the genera Ascocoryne , Cadophora and Neobulgaria , which have potential impacts on wood quality (discoloration and decay). Beta diversity analyses revealed that wood type was the primary driver of community composition. These findings provide insights into the spatial organization of fungal communities within wood from living Populus trees and highlight the need for mechanistic studies of heartwood mycobiome assembly and its implications for wood quality in plantation forestry.