A preliminary examination of the bacterial, archaeal, and fungal rhizosphere microbiome in healthy and Phellinus noxius-infected trees.

Phellinus noxius is a pathogenic fungus that causes brown root rot disease, resulting in a widespread tree and crop mortality in the tropics and subtropics. Early stages of this disease are largely asymptomatic, hindering early diagnosis and effective treatment. We hypothesized that P. noxius infection would alter the rhizosphere microbiome of infected trees, based on which diagnostic biomarkers could be developed. Here, we examined for the first time the bacterial, archaeal, and fungal rhizosphere microbiome in four species of healthy and P. noxius-infected trees (Ficus microcarpa, Celtis sinensis, Mallotus paniculatus, and Cinnamomum camphora) using high-throughput amplicon sequencing. Results revealed the dominance of Proteobacteria and Actinobacteria in bacteria, Crenarchaeota and Euryarchaeota in archaea, and Ascomycota and Basidiomycota in fungi. Phellinus noxius infection did not affect the alpha diversity of the bacterial rhizosphere microbiome in all four tree species but affected that of archaea and fungi in a tree species-dependent manner. Infection with P. noxius only affected the bacterial rhizosphere composition in M. paniculatus but not the other three tree species. By contrast, P. noxius infection affected the composition of the archaeal and fungal rhizosphere microbiome in all four tree species. Collectively, these results suggest that potential diagnostic biomarkers for brown root rot disease are tree species-specific and should be developed based on different taxonomic groups. Our study has provided insights into the rhizosphere microbiome in healthy and P. noxius-infected trees and laid a solid foundation for future comprehensive studies.