Keywords: 
• endophytic bacteria /
• diversity /
• similarity coefficient /
• Bacillus /
• Dendrobium sinense populations

Abstract: Endophytic bacteria are equally important as mycorrhizal fungi for orchid plant species in the ecological process of seed germination and seedling establishment. To investigate diversity of endophytic bacteria associated with Dendrobium sinense,inhabiting tropical forest in Hainan Island,root samples were collected for bacteria culturing,DNA extraction,16 S rDNA amplification,and sequencing. A total of 130 strains of endophytic bacteria were isolated from the roots of D. sinense in Jianfengling,Bawangling and Diaoluoshan mountains. Phylogenetic analysis of 16 S rDNA sequences revealed that the roots-associated endophytic bacteria community was comprised of 15 species of 7 genera: Bacillus,Burkholderia,Pantoea,Enterobacter,Luteibacter,Serratia and Cedecea. Of these bacteria,Bacillus is the most frequently isolated endophytic bacterium,followed by Enterobacter and Burkholderia. All the Bacillus spp. occurred in the three habitats at a roughly equal frequency. Compositional similarity of endophytic bacterial community associated with D. sinense is highest in between the Bawangling and Diaoluoshan mountains,where similarity is lowest in their environmental factors but highest in their host plant species composition is highest in similarity. This suggests that the difference in host plants is responsible for the difference in endophytic bacterial species composition of the roots of the host plants.