Rhizobacteria emit bioactive metabolites with antifungal properties that could be used for biocontrol of fungal diseases. In this study, we evaluated the potential of diffusible and volatile organic compounds (VOCs) emitted by avocado rhizobacteria to inhibit the growth of Fusarium kuroshium, one of the causal agents of Fusarium dieback (FD) in avocado. Three bacterial isolates (INECOL-6004, INECOL-6005, and INECOL-6006), belonging to the Bacillus genus, were selected based on their capacity to inhibit several avocado fungal pathogens, and tested in antagonism assays against F. kuroshium. The three bacterial isolates significantly inhibited F. kuroshium mycelial growth by up to 48%. The composition of bacterial diffusible compounds was characterized by the analysis of EtOAc and n-BuOH extracts by using ultra-performance liquid chromatography (UPLC) coupled to high-resolution mass spectrometry (HRMS). The three bacterial isolates produced cyclo-lipopeptides belonging to the iturin, fengycin, and surfactin families. The antifungal activity of n-BuOH extracts was larger than that of EtOAc extracts, probably due to the greater relative abundance of fengycin in the former than in the latter. In addition, isolates INECOL-6004 and INECOL-6006 significantly inhibited F. kuroshium mycelial growth through VOC emission by up to 69.88%. The analysis of their VOC profiles by solid phase micro-extraction (SPME) coupled to gas chromatography and mass spectrometry (GC-MS) revealed the presence of ketones and pyrazine compounds, particularly of 2-nonanone, which was not detected in the VOC profile of isolate INECOL-6005. These results emphasize the need to further investigate the antifungal activity of each bioactive compound for the development of new formulations against fungal phytopathogens.

中文翻译：

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鳄梨根际细菌产生的可扩散和挥发性有机化合物对黑镰刀菌具有抗真菌作用

根际细菌释放出具有抗真菌特性的生物活性代谢物，可用于真菌疾病的生物防治。在这项研究中，我们评估了鳄梨根际细菌排放的可扩散和挥发性有机化合物 (VOC) 抑制黑镰刀菌生长的潜力，黑镰刀菌是鳄梨枯萎病 (FD) 的致病因子之一。三种属于芽孢杆菌属的细菌分离株（INECOL-6004、INECOL-6005 和 INECOL-6006）是根据它们抑制几种鳄梨真菌病原体的能力进行选择的，并在对 F. kuroshium 的拮抗试验中进行了测试。这三种细菌分离物显着抑制了 F. kuroshium 菌丝体的生长，最高可达 48%。通过使用超高效液相色谱 (UPLC) 与高分辨率质谱 (HRMS) 分析 EtOAc 和 n-BuOH 提取物来表征细菌可扩散化合物的组成。三种细菌分离物产生属于伊图林、芬霉素和表面活性素家族的环脂肽。n-BuOH 提取物的抗真菌活性大于 EtOAc 提取物的抗真菌活性，这可能是因为前者中的芬霉素相对丰度高于后者。此外，分离株 INECOL-6004 和 INECOL-6006 通过 VOC 排放显着抑制 F. kuroshium 菌丝体生长，最高可达 69.88%。通过固相微萃取 (SPME) 与气相色谱和质谱 (GC-MS) 联用对其 VOC 的分析表明存在酮和吡嗪化合物，特别是 2-壬酮，在分离株 INECOL-6005 的 VOC 谱中未检测到。这些结果强调需要进一步研究每种生物活性化合物的抗真菌活性，以开发针对真菌植物病原体的新制剂。