Stem end rot (SER) disease caused by Alternaria alternata is one of the main fungal diseases in pitaya and other crops in Nam Dinh, Vietnam, that leads to extensive yield and economic losses. Biocontrol of SER, using endophytic bacteria, is environmentally friendly and compatible with other control measures. Hence, it is emerging as an alternative disease management strategy in sustainable agriculture. This study aimed to screen antagonistic bacteria isolated from the weed, Eleusine indica, with the potential to manage SER. A total of 16 endophytes were isolated from the stems, leaves, and roots of the weed, E. indica. Of those, 6 strains presented antagonistic effects against A. alternata growth, and one isolate, EI-15, showed a significant inhibitory effect on SER. In addition, analyzing the 16S rDNA sequence indicated that EI-15 was a strain of Bacillus amyloliquefaciens. Moreover, the results of the antagonistic spectrum assay showed that EI-15 significantly inhibited some plant and fruit tree pathogens, especially the suppression of A. alternata. Notably, the culture filtrate of strain EI-15 exhibited in vitro apparent activity against A. alternata. Furthermore, an in vivo antagonistic experiment of EI-15 on pitaya twig showed a significant reduction of lesion on twigs than the control. Overall, this study suggested the potential application of the EI-15 strain as a biological agent and needs to be further studied in the field to control SER.

中文翻译：

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从杂草植物中分离出的内生细菌可作为对抗越南火龙果茎端腐病病原体的潜在生物防治剂

由链格孢引起的茎端腐病（SER）病是越南南定火龙果和其他作物的主要真菌病害之一，导致大量的产量和经济损失。使用内生细菌对 SER 进行生物防治，对环境友好且与其他防治措施兼容。因此，它正在成为可持续农业中的替代疾病管理策略。本研究旨在筛选从杂草 Eleusine indica 中分离出的具有控制 SER 潜力的拮抗细菌。从杂草 E. indica 的茎、叶和根中分离出总共 16 种内生菌。其中，6 株表现出对抗 A.alternata 生长的拮抗作用，一种分离株 EI-15 对 SER 表现出显着的抑制作用。此外，分析 16S rDNA 序列表明 EI-15 是一株解淀粉芽孢杆菌。此外，拮抗谱测定结果表明，EI-15 对一些植物和果树病原体有显着抑制作用，尤其是对 A. alternata 的抑制作用。值得注意的是，菌株 EI-15 的培养滤液表现出抗 A.alternata 的体外表观活性。此外，EI-15 对火龙果树枝的体内拮抗实验表明，与对照相比，树枝上的病变显着减少。总的来说，这项研究表明 EI-15 菌株作为生物制剂的潜在应用，需要在该领域进一步研究以控制 SER。尤其是抑制 A. alternata。值得注意的是，菌株 EI-15 的培养滤液表现出抗 A.alternata 的体外表观活性。此外，EI-15 对火龙果树枝的体内拮抗实验表明，与对照相比，树枝上的病变显着减少。总的来说，这项研究表明 EI-15 菌株作为生物制剂的潜在应用，需要在该领域进一步研究以控制 SER。尤其是抑制 A. alternata。值得注意的是，菌株 EI-15 的培养滤液表现出抗 A.alternata 的体外表观活性。此外，EI-15 对火龙果树枝的体内拮抗实验表明，与对照相比，树枝上的病变显着减少。总的来说，这项研究表明 EI-15 菌株作为生物制剂的潜在应用，需要在该领域进一步研究以控制 SER。