In this study, 18 plant growth-promoting bacterial (PGPB) strains were isolated from the rhizosphere of both Red silk-cotton tree ( Bombax malabaricum ) and Chinese banyan (Ficus retusa) . Culture morphology was observed and genotypic characterization was accomplished by sequencing partial 16S rRNA gene. Plant growth promotion traits and antagonistic activities of the strains against phytopathogenic fungi were evaluated. Among all strains, Bacillus thuringiensis (MN419208) exert the highest indole acetic acid (38 µg/ml), produced exopolysaccharides (587.2 µg/ml), and fixed nitrogen which in turn increased both fresh and dry weights of bean plants by 41.5% and 18.8%, respectively. In another greenhouse experiment studying the antifungal activities of seven strains and their co-culture against Rhizoctonia solani (LN735538), B. sonorensis MN419205, B. wiedmannii MN419207, B. subtilis MN419218, and the mixture of (MN419207) and (MN419208) reduced total damping off from 81.7% in control to 30%, 35%, 35%, and 38.3%, respectively, and reduced disease severity index from 33.3% to 20.5%, 22.5%, 14.2%, and 19.3% as well. Our data indicate that these strains are effective in promoting plant growth and in inhibiting R. solani infection nonetheless field experiments are needed to examine their effectiveness as a viable alternative to chemical fertilizers and conventional pesticides.

中文翻译：

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有效抑制蚕豆根腐病的植物促生菌的分离鉴定

本研究从红丝棉树（Bombax malabaricum）和榕树（Ficus retusa）的根际分离出18株植物促生长菌（PGPB）菌株。观察培养物形态并通过对部分 16S rRNA 基因进行测序来完成基因型表征。评价了菌株对植物病原真菌的植物生长促进性状和拮抗活性。在所有菌株中，苏云金芽孢杆菌 (MN419208) 发挥最高的吲哚乙酸 (38 µg/ml)、产生胞外多糖 (587.2 µg/ml) 和固定氮，进而使豆类植物的鲜重和干重均增加 41.5% 和分别为 18.8%。在另一个温室实验中，研究了七个菌株的抗真菌活性及其对立枯丝核菌 (LN735538​​) 的共培养，B.sonorensis MN419205，B. wiedmannii MN419207、B. subtilis MN419218 以及 (MN419207) 和 (MN419208) 的混合物将总衰减从对照的 81.7% 分别降低到 30%、35%、35% 和 38.3%，并降低了疾病严重程度指数33.3% 到 20.5%、22.5%、14.2% 和 19.3%。我们的数据表明，这些菌株在促进植物生长和抑制茄病菌感染方面是有效的，但仍需要进行田间试验来检验它们作为化肥和常规杀虫剂的可行替代品的有效性。