Fungal stem end rot disease of pitaya caused by Alternaria alternata is one of the most destructive diseases in Binh Thuan province, Vietnam. This study aimed to assess the antagonistic effects of some endophytic bacteria isolated from the weed plant (Echinochloa colonum) against A. alternata. A total of 19 endophytic bacteria were isolated and 5 of them presented in vitro antagonistic activity against A. alternata. Of five, strain EC80 significantly inhibited the pathogenic growth with a mean inhibition diameter of 11.88 ± 0.08 mm, while the other four (C79, EC83, EC90, and EC97) showed a weak inhibition. Interestingly, the combination of EC79 and EC80 reduced more biomass of pathogenic fungi than the single one did. EC79 showed positive results for amylase, indole acetic acid (IAA), and biofilm production, whereas EC80 presented positive capabilities for IAA and biofilm production and a negative one for amylase production. In addition, the combined filtrate of EC79 and EC80 presented non-antifungal activity on biocontrol tests in vitro, indicating that bacteria cells played a role in defending against the pathogen. Moreover, both isolates EC79 and EC80 significantly increased seedling biomass than the control. The results suggest that those two strains in combination had the potential to be used as a biocontrol agent against A. alternata. More studies should be done in the future to evaluate their efficiency under the field conditions.

中文翻译：

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越南杂草植物内生细菌对火龙果茎端腐烂病原菌的拮抗活性

由交链孢霉引起的火龙果真菌茎端腐烂病是越南平顺省最具破坏性的疾病之一。这项研究旨在评估从杂草植物（Echinochloa Colonum）中分离出的一些内生细菌对交链曲霉的拮抗作用。总共分离出19种内生细菌，其中5种具有体外对链球菌的拮抗活性。在五种中，菌株EC80显着抑制了病原体的生长，平均抑制直径为11.88±0.08 mm，而其他四种（C79，EC83，EC90和EC97）则表现出微弱的抑制作用。有趣的是，EC79和EC80的组合比单个真菌减少了更多的病原真菌生物量。EC79在淀粉酶，吲哚乙酸（IAA）和生物膜生产方面显示出积极的成果，而EC80在IAA和生物膜生产方面表现出积极的能力，而在淀粉酶生产方面则表现出消极的能力。此外，EC79和EC80的合并滤液在体外生物控制测试中显示出非抗真菌活性，表明细菌细胞在防御病原体方面发挥了作用。而且，分离株EC79和EC80均显着增加了幼苗的生物量。结果表明，这两种菌株的组合具有被用作对抗链球菌的生物防治剂的潜力。将来应进行更多研究，以评估它们在现场条件下的效率。表明细菌细胞在防御病原体方面发挥了作用。而且，分离株EC79和EC80均显着增加了幼苗的生物量。结果表明，这两种菌株的组合具有被用作对抗链球菌的生物防治剂的潜力。将来应进行更多研究，以评估它们在现场条件下的效率。表明细菌细胞在防御病原体方面发挥了作用。而且，分离株EC79和EC80均显着增加了幼苗的生物量。结果表明，这两种菌株的组合具有被用作对抗链球菌的生物防治剂的潜力。将来应进行更多研究，以评估它们在现场条件下的效率。