Ectomycorrhizal and saprotrophic fungi are linked to reduced pathogenic fungi across roots and rhizosphere soils of major afforestation species in northeastern China

Abstract

Plants can enhance their resistance to pathogens by regulating their associated microbial communities, which contributes to the ecological adaptability and potential application of afforestation species. However, microbial interactions in the rhizosphere and roots, and their implications for pathogen suppression in afforestation systems, remain unclear. In this study, we investigated the structure and potential functions of bacterial and fungal communities in roots, rhizosphere soil, and bulk soil of major afforestation species in northeastern China, Birch, Larch, and Poplar, using amplicon sequencing, with a particular focus on associations among functional microbial groups. In rhizosphere soils, the relative abundance of ectomycorrhizal (EcM) fungi was negatively correlated with that of pathogenic fungi in Birch and Larch forests. In roots, the relative abundance of saprotrophic fungi was negatively correlated with that of pathogenic fungi across all tree species. In contrast, major bacterial genera showed no consistent associations with pathogen abundance across compartments. Additionally, Larch forests showed a greater influx of bacterial and fungal taxa from the rhizosphere into the roots, yet root pathogen abundance remained comparatively low. These results suggest that negative associations between pathogenic fungi and EcM fungi in the rhizosphere, together with compartment specific microbial filtering and negative associations with saprotrophic fungi within roots, may contribute to reduced abundance of pathogenic fungi particularly in Larch. These results highlight the potential role of host-associated microbial community structure in mediating pathogen pressure and enhancing the ecological adaptability of afforestation species.

Graphical abstract

Keywords

tree species / rhizosphere / fungal functional groups / microbial colonization

Highlight

	● EcM fungi were negatively associated with pathogens in the rhizosphere.
	● Saprotrophic fungi were negatively associated with pathogens in roots.
	● Bacterial taxa showed no consistent pathogen linked patterns.
	● Strong rhizosphere to root microbial filtering occurred in Larch.
	● Compartment specific microbial structure may regulate pathogen pressure.

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