Rhizosphere and endophytic bacterial communities of the endangered alpine modest primrose and their plant growth-promoting potential.

Plant microbiomes play critical roles in host growth and stress resilience, yet remain underexplored in alpine ecosystems. We investigated the rhizosphere and endophytic bacterial communities of an endangered alpine modest primrose (Primula modesta var. hannasanensis), which is endemic to the high-altitude regions of Korea. Using 16 S rRNA gene amplicon sequencing, we compared the bacterial communities in wild and cultivated populations. The rhizosphere microbiota exhibited greater diversity than the root endophytes, and cultivated plants harbored more diverse and compositionally distinct endophytic communities than wild plants, suggesting that cultivation influences the microbial structure. We isolated bacterial strains from these communities and identified Leifsonia lichenia JBCE310 and Chryseobacterium piperi JBCE316 as significantly enhancing seed germination and seedling growth of Primula malacoides and Arabidopsis thaliana. The co-inoculation yielded synergistic effects that were likely mediated by phytohormone production. These results highlight the functional potential of alpine plant-associated bacteria and provide potential microbial candidates for the conservation and ex situ propagation of endangered alpine flora.