Abstract:[Background] Populus tomentosa, belonging to the family Salicaceae, is a deciduous large tree. It has a wide planting area in China and is characterized by fast growth, high reproductive rate, and strong environmental adaptability. Exploring the characteristics and functions of endophytic bacteria from P. tomentosa holds significant guidance for agricultural production. [Objective] To explore the functional diversity of endophytic bacteria in P. tomentosa and provide excellent bacterial resources for efficient agricultural production. [Methods] We used DN, LB, CCM, and NA media to isolate endophytic bacteria from various tissues of the fast-growing plant P. tomentosa. The 16S rRNA gene sequences of the bacterial strains were determined and used to build a phylogenetic tree. Potential plant growth-promoting characteristics such as nitrogen fixation, phosphorus solubilization, potassium release, siderophore production, and indole-3-acetic acid (IAA) production of the strains were explored. The biochemical characteristics of the strains were determined. The strains with strong growth-promoting effects were selected for rice seed germination and rice pot experiments. [Results] A total of 16 representative bacterial strains were isolated, among which 6, 6, 7, 6, and 11 strain had the abilities of solubilizing phosphorus, releasing potassium, fixing nitrogen, producing IAA, producing siderophores, respectively. This result indicated the rich functional diversity of endophytic bacteria in P. tomentosa. The results from rice seed germination and growth promotion experiments showed that 4 single strains and 2 strain combinations promoted rice germination and growth. The combination of Enterobacter soli BYG3205 with Phytobacter ursingii BYG3102 or Acinetobacter soli BYJ201 showed better effect than single strain treatments. [Conclusion] A total of 16 strains of endophytic bacteria were isolated from P. tomentosa, and their characteristics were analyzed through 16S rRNA gene sequencing, nitrogenase activity determination, phosphate solubilization, potassium solubilization, and auxin production. Selected bacterial strains with growth-promoting effects exhibited positive effects in rice pot experiments. These endophytic bacteria enriched the microbial resources and provided a feasible approach for green and sustainable agriculture.
