BACKGROUNDFusarium oxysporum f. sp. cucumerinum and Rhizoctonia solani AG‐4 are the two most important fungal pathogens causing soil‐borne fungal diseases of cucumber; they are difficult to control and cause serious economic losses. Given the detrimental effects of the indiscriminate use of chemical fungicides, biocontrol emerges as an efficient and ecofriendly alternative for managing soil‐borne fungal diseases.RESULTSStreptomyces lydicus JCK‐6019 (hereafter, JCK‐6019) was isolated from rhizosphere soil. Its fermentation filtrate and volatile organic compounds exhibited broad‐spectrum antifungal activity against various phytopathogenic fungi and oomycetes. JCK‐6019 produced natamycin as an agar‐diffusible antifungal metabolite. It also produced indole‐3‐acetic acid and various hydrolytic enzymes. In vivo experiments revealed that a ten‐fold‐diluted optimized JCK‐6019 fermentation broth exhibited 100% control efficiency against cucumber damping‐off disease and 62.5% control efficiency against cucumber Fusarium wilt disease. Pretreatment of cucumber seedlings with 1000‐fold‐diluted optimized JCK‐6019 fermentation broth resulted in 68.18% and 23.91% disease control values against cucumber damping‐off and Fusarium wilt disease, respectively. Moreover, peroxidase activity in cucumbers after 1 day of treatment was 1.5‐fold higher than that in the control. Similarly, polyphenol oxidase activity in cucumbers after 3 days of treatment was 2.34‐fold higher than that in the control, indicating that JCK‐6019 can induce plant resistance.CONCLUSIONThe natamycin‐producing strain JCK‐6019 could effectively suppress the development of cucumber Fusarium wilt and damping‐off disease by inducing plant resistance and producing antifungal metabolites, including natamycin and volatile organic compounds. Thus, JCK‐6019 possesses high potential for application in the development of biocontrol agents against soil‐borne fungal diseases of cucumber. © 2024 Society of Chemical Industry.

中文翻译：

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产纳他霉素的 Streptomyces lydicusJCK-6019 对黄瓜土传真菌病害的生物防治潜力及其生物防治机制的表征


背景尖孢菌 f. sp. 黄瓜和立枯丝核菌 AG-4 是导致黄瓜土壤传播真菌病害的两种最重要的真菌病原体;它们难以控制，造成严重的经济损失。鉴于不加选择地使用化学杀菌剂的有害影响，生物防治成为管理土壤传播真菌病害的一种高效且环保的替代方案。结果从根际土壤中分离出 Streptomyces lydicus JCK-6019 （以下简称 JCK-6019）。其发酵滤液和挥发性有机化合物对各种植物病原真菌和卵菌表现出广谱抗真菌活性。JCK-6019 产生纳他霉素作为琼脂可扩散的抗真菌代谢物。它还产生吲哚-3-乙酸和各种水解酶。体内实验表明，10 倍稀释的优化 JCK-6019 发酵液对黄瓜阻尼病的控制效率为 100%，对黄瓜镰刀菌枯萎病的控制效率为 62.5%。用 1000 倍稀释的优化 JCK-6019 发酵液对黄瓜幼苗进行预处理，对黄瓜阻尼和镰刀菌枯萎病的病害控制值分别为 68.18% 和 23.91%。此外，处理 1 天后黄瓜的过氧化物酶活性比对照高 1.5 倍。同样，黄瓜处理 3 天后多酚氧化酶活性比对照高 2.34 倍，表明 JCK-6019 可以诱导植物抗性。结论产纳他霉素菌株 JCK-6019 通过诱导植物抗性并产生抗真菌代谢物（包括纳他霉素和挥发性有机化合物）来有效抑制黄瓜镰刀菌枯萎病的发展和抑制病害。因此，JCK-6019 在开发针对黄瓜土壤真菌病害的生物防治剂方面具有很高的应用潜力。© 2024 化工学会.