Bacillus spp. have a wide range of activities in the biocontrol potential against various phytopathogens. This study focuses on the biocontrol potential of two species belonging to the same genera, as Bacillus subtilis (SSR2I) and Bacillus flexus (AIKDL) have contrasting activity under in vivo and in vitro conditions. In this study, two medicinal plants-associated bacteria showing antagonistic activity against wilt-causing pathogens were selected and identified as B. subtilis (SSR2I) and B. flexus (AIKDL) based on 16S rRNA gene sequencing. Crude extracts of these bacteria showed that chloroform extracts of AIKDL, and ethyl acetate extraction of SSR2I showed effective potential inhibition of both the wilt-causing pathogens in the well-diffusion method. PCR-based detection of antimicrobial peptide genes revealed the presence of five genes in B. subtilis and none in B. flexus. On the basis of in vivo analysis, the isolate SSR2I showed reduced disease incidence and enhanced biocontrol efficiency against Ralstonia solanacearum and Fusarium oxysporum compared with AIKDL and control plants. Further, the isolates SSR2I also enhanced the induced systemic resistance (ISR) against both the pathogens compared to the control. However, the isolate AIKDL showed enhanced ISR against F. oxysporum-treated plants, but not against R. solanacearum-treated plants. The results indicated that even though the isolates had strong antagonistic potential under in vitro conditions, their biocontrol efficiency differed in in vivo condition. On the basis of the overall performance, the isolate SSR2I could be formulated as biocontrol agents against both the wilt-causing pathogens tested in this study.

中文翻译：

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生物防治芽孢杆菌对植物生长促进和系统诱导对细菌和真菌枯萎病病原体的抗性潜力的评价

芽孢杆菌属 在针对各种植物病原体的生物防治潜力方面具有广泛的活性。本研究侧重于属于同一属的两个物种的生物防治潜力，因为枯草芽孢杆菌 (SSR2I) 和弯曲芽孢杆菌 (AIKDL) 在体内和体外条件下具有对比活性。在本研究中，基于 16S rRNA 基因测序，选择了两种对引起枯萎病的病原体具有拮抗活性的药用植物相关细菌并鉴定为枯草芽孢杆菌 (SSR2I) 和弯曲芽孢杆菌 (AIKDL)。这些细菌的粗提取物表明，AIKDL 的氯仿提取物和 SSR2I 的乙酸乙酯提取物在良好扩散方法中显示出对两种引起枯萎病的病原体的有效潜在抑制。基于 PCR 的抗菌肽基因检测揭示了 B. subtilis 和 B. flexus 中没有。根据体内分析，与 AIKDL 和对照植物相比，分离株 SSR2I 对青枯病菌和尖孢镰刀菌的发病率降低，生物防治效率提高。此外，与对照相比，分离株 SSR2I 还增强了对两种病原体的诱导系统抗性 (ISR)。然而，分离株 AIKDL 对尖孢镰刀菌处理的植物表现出增强的 ISR，但对青枯菌处理的植物则没有。结果表明，尽管分离株在体外条件下具有很强的拮抗潜力，但它们在体内条件下的生防效率存在差异。根据整体性能，分离株 SSR2I 可以配制成生物防治剂，对抗本研究中测试的两种引起萎蔫的病原体。