The present study assessed the plant growth-promoting (PGP) traits and diversity of culturable rhizobacteria associated with guarana (Paullinia cupana), a typical tropical plant. Ninety-six bacteria were isolated, subjected to biochemical tests, and identified by partial or total 16S rDNA sequencing. Proteobacteria and Firmicutes were the dominant rhizospheric phyla found, and Burkholderia and Bacillus were the most abundant genera. Thirteen strains exhibited the four PGP traits evaluated, and most of them belonged to the genus Burkholderia. Two multi-trait PGP strains, RZ2MS9 (Bacillus sp.) and RZ2MS16 (Burkholderia ambifaria), expressively promoted corn and soybean growth under greenhouse conditions. Compared to the non-inoculated control, increases in corn root dry weight of 247.8 and 136.9% were obtained with RZ2MS9 and RZ2MS16 inoculation, respectively, at 60 days after seeding. The dry weights of corn and soybean shoots were significantly higher than those of non-inoculated plants, showing increases of more than 47% for both strains and crops. However, soybean root dry weight did not increased after bacterial inoculation with either strain. The colonization behavior of RZ2MS16 was assessed using GFP-labeling combined with fluorescence microscopy and a cultivation-based approach for quantification. RZ2MS16:gfp was able to colonize the roots and shoots of corn and soybean, revealing an endophytic behavior.

本研究评估了典型的热带植物瓜拉那（Paullinia cupana）的植物促生长（PGP）特性和可培养根瘤菌的多样性。分离出九十六种细菌，进行生化测试，并通过部分或全部16S rDNA测序进行鉴定。变形杆菌和Firmicutes是根际上最主要的种，伯克霍尔德菌和芽孢杆菌是最丰富的属。13个菌株表现出所评估的四个PGP性状，其中大多数属于伯克霍尔德氏菌属。两种多性状PGP菌株RZ2MS9（芽孢杆菌）和RZ2MS16（冈比亚伯克霍尔德菌）），在温室条件下显着促进了玉米和大豆的生长。与未接种的对照相比，接种RZ2MS9和RZ2MS16后，在播种后60天分别获得了247.8％和136.9％的玉米根干重。玉米和大豆新芽的干重明显高于未接种植物的干重，品系和农作物的干重均增加了47％以上。但是，用任一菌株进行细菌接种后，大豆根的干重均未增加。RZ2MS16的定殖行为使用GFP标记结合荧光显微镜和基于培养的定量方法进行评估。RZ2MS16：gfp能够在玉米和大豆的根和芽上定植，显示出内生行为。