Comparative analysis of root microbiomes in four Swertia species from Taiwan.

Swertia (Gentianaceae) comprises four species endemic to Taiwan that possess significant medicinal potential. While root microbiomes are known to promote plant adaptation, the microbial ecology of Taiwanese Swertia remains largely unexplored. We investigated the rhizosphere and root endosphere microbiomes of these species using 16S rRNA gene sequencing and predictive functional profiling, integrated with host phylogenetic data. Our results revealed that rhizosphere bacterial communities were significantly more diverse than those in the root endosphere. PERMANOVA indicated that host species and plant compartment significantly influenced bacterial communities, but the high residual variance suggests that much of the community variation remains unexplained by the variables measured in this study. Phylogenetic analysis indicated that the root endosphere is more strongly influenced by host phylogeny, with closely related species harboring more similar communities. Functional profiling further demonstrated that the rhizosphere is predicted to be enriched in pathways related to nitrogen fixation and organic matter degradation, whereas the endosphere harbors bacterial taxa potentially associated with pathogen suppression. These findings underscore the multifaceted roles of the root microbiome in supporting the development, stress adaptation, and ecosystem sustainability of Swertia species in Taiwan's unique altitudinal gradients.