Endophytes are beneficial plant microbes which help the plants by producing various plant growth promoting substances and also by acting as biocontrol agents against various plant pathogens. In the present study, evaluation of endophytic bacteria isolated from Gnetum gnemon, an ethnomedicinal plant was carried out for their plant growth promoting (PGP) activity and antagonistic potential against bacterial wilt pathogen Ralstonia solanacearum. Initially a total of 40 endophytic bacteria were isolated which were clustered into 13 groups based on RFLP and BOX-PCR fingerprinting. These 13 representative isolates belonged to different genera of Bacillus (9), Solibacillus (1), Staphylococcus (2) and Caballeronia (1). Among them, six isolates were positive for production of IAA, the value of which ranged from 11.16 to 27.63 μg mL⁻¹. Phosphate solubilisation in the range of 106.4 to –212.7 μg mL⁻¹ was shown by three isolates. Eight isolates producedammonia, the value of which ranged from 1.3 to 6.1 μmol mL⁻¹. All tested isolates were positive for siderophore production. For extracellular enzyme production, 7 isolates were positive for protease, 8 for cellulase and 10 for amylase production. The isolates were also tested for their antagonistic activity against R. solanacearum in vitro and in planta assay using tomato seedlings. Staphylococcus warneri GL1 showed the highest biocontrol efficacy of 77.67 % followed by Bacillus velezensis GL3 i.e. 70.1 %. R. solanacearum antagonistic isolates were analysed for the presence of antimicrobial peptide biosynthesis genes bmyB, srfAA, fenD and ituC. All the antagonistic isolates showed the presence of all four genes, except the isolate Bacillus velezensis GMC2, where the gene for fengycin synthetase (fenD) was absent. Based on in vitro PGP traits, three isolates Bacillus velezensis GL3, Bacillus atrophaeus GMC1 and Bacillus megaterium GS2 were selected, these three endophytic bacteria individually and their consortia were tested for in planta PGP activities in tomato plants. Application of Bacillus velezensis GL3 alone and consortia of three isolates showed significant improvement in growth parameters such as shoot length, fresh weight and dry weight in a pot experiment. Colonization of endosphere of treated tomato seedlings by the endophytic isolate Bacillus velezensis GL3 was confirmed by visualization of colony morphology and BOX-PCR fingerprinting. Our study highlights the potential of endophytes associated with unexplored plants like G. gnemon for development of bioformulation aimed at enhancing plant growth and bacterial wilt disease control.

内生细菌是有益的植物微生物，其通过产生各种植物生长促进物质并且还通过充当针对各种植物病原体的生物防治剂来帮助植物。在本研究中，对从民族植物Gnetum gnemon分离的内生细菌进行了植物生长促进（PGP）活性和对枯萎病青枯菌Ralstonia solanacearum的拮抗潜力的评价。最初，共分离出40种内生细菌，根据RFLP和BOX-PCR指纹图谱将其分为13组。这13个代表性分离株分别属于芽孢杆菌（9），索利比克斯菌（1），葡萄球菌（2）和卡瓦列罗尼亚（1）。其中，有6株IAA产生呈阳性，其值在11.16至27.63μgmL ^-1之间。三种分离物显示磷酸盐溶解度在106.4至–212.7μgmL ^-1范围内。八个分离物产生氨，其值在1.3至6.1μmolmL ^-1之间。所有测试的分离物对铁载体产生呈阳性。对于细胞外酶生产，蛋白酶的阳性菌株有7种，纤维素酶是8株，淀粉酶是10株。还使用番茄幼苗在体外和植物检定中测试了分离株对青枯菌的拮抗活性。金黄色葡萄球菌GL1表现出最高的生物防治功效，为77.67％，其次是维氏芽孢杆菌GL3，即70.1％。分析了青枯菌拮抗菌株的抗菌肽生物合成基因bmyB，srfAA，fenD和ituC的存在。除了拮抗芽孢杆菌GMC2（不存在丰霉素合成酶（fen D）的基因）外，所有拮抗菌株均显示所有四个基因的存在。基于体外PGP性状，株3芽孢杆菌velezensis GL3，萎缩芽孢杆菌GMC1和巨大芽孢杆菌选择GS2，分别测试这三种内生细菌及其菌群在番茄植株中植物PGP活性中的含量。在盆栽实验中，单独使用维氏芽孢杆菌GL3和三个分离株的组合显示出生长参数的显着改善，例如枝长，鲜重和干重。通过菌落形态的可视化和BOX-PCR指纹图谱，证实了内生分离株velezensis GL3对处理过的番茄幼苗内球的定殖。我们的研究突出了与未开发的植物（如G. gnemon）相关的内生菌在开发旨在提高植物生长和控制细菌性枯萎病的生物制剂方面的潜力。