Tobacco Research Institute, CAAS/Key Laboratory of Tobacco Pest Monitoring, Controlling, and Integrated Management, Qingdao, China.
Shanghai Tobacco Group Material Procurement Center, Shanghai, China.
Appl Environ Microbiol. 2023 Feb 28;89(2):e0189222. doi: 10.1128/aem.01892-22. Epub 2023 Feb 1.
Tobacco bacterial wilt, which is caused by Ralstonia solanacearum, is a devastating soilborne disease of tobacco worldwide and is widespread in the continuously acidic fields of southern China. Here, the fumigation activity under different pH conditions, component identification, and bioactivity of the volatile organic compounds (VOCs) produced by an acid-tolerant strain, Pseudomonas protegens CLP-6, were investigated. There was a wide antimicrobial spectrum of the VOCs against phytopathogens, including four bacteria, eight fungi, and two oomycetes. The antagonistic activity of the VOCs against R. solanacearum was proportionally correlated with the concentration of the inoculum, amount, culture time, and culture pH for CLP-6. The number of gene copies of R. solanacearum was significantly inhibited by VOCs produced at pH 5.5 . The control effect of VOCs emitted at pH 5.5 was 78.91% for tobacco bacterial wilt, which was >3-fold greater than that at pH 7.0. Finally, the main volatile compounds were identified by solid-phase microextraction (SPME)-gas chromatography-mass spectroscopy (GC-MS) as -methyl thioacetate, methyl thiocyanate, methyl disulfide, 1-decene, 2-ethylhexanol, 1,4-undecadiene, 1-undecene, 1,3-benzothiazole, and 2,5-dimethylpyrazine, and the inhibition rates of 1,3-benzothiazole, 2-ethylhexanolmethyl thiocyanate, dimethyl disulfide, and -methyl thioacetate were 100%, 100%, 88.91%, 67.64%, and 53.29%, respectively. -Methyl thioacetate was detected only at pH 5.5. In summary, VOCs produced by P. protegens CLP-6 had strong antagonistic activities against phytopathogens, especially R. solanacearum, under acidic conditions and could be used to develop a safe and additive fumigant against R. solanacearum on tobacco and even other crop bacterial wilt diseases in acidic fields. VOCs produced by beneficial bacteria penetrate the rhizosphere to inhibit the growth of plant-pathogenic microorganisms; thus, they have the potential to be used as biological agents in controlling plant diseases. Tobacco bacterial wilt, which is caused by the acidophilic pathogen R. solanacearum, is a major bacterial disease in southern China and is prevalent in acidic soil. In this study, we discovered that the VOCs produced by P. protegens CLP-6 had excellent inhibitory effects on important plant pathogens. Moreover, two of the VOCs, namely, 1,3-benzothiazole and 2-ethylhexanol, had excellent inhibitory effect on R. solanacearum, and another VOC substance, methyl thiocyanate, was produced only at pH 5.5. The VOCs produced by the acid-tolerant strain P. protegens CLP-6 may have potential as environment-friendly microbial fumigant agents for bacterial wilt of tobacco or even other crops in acidic soils in China.
烟草青枯病是一种由青枯雷尔氏菌引起的毁灭性土传病害，在全球范围内广泛存在于烟草种植区，在中国南方持续酸化的土壤中也很普遍。本研究旨在探讨在不同 pH 值条件下，耐酸菌株恶臭假单胞菌 CLP-6 产生的熏蒸活性、成分鉴定和挥发性有机化合物（VOCs）的生物活性。这些 VOCs 对包括四种细菌、八种真菌和两种卵菌在内的植物病原菌具有广谱的抑菌活性。VOCs 对青枯雷尔氏菌的拮抗活性与 CLP-6 的接种物浓度、数量、培养时间和培养 pH 值成正比。在 pH 值为 5.5 时，VOCs 显著抑制青枯雷尔氏菌的基因拷贝数。在 pH 值为 5.5 时，VOCs 对烟草青枯病的防治效果为 78.91%，比 pH 值为 7.0 时高出 3 倍以上。最后，通过固相微萃取（SPME）-气相色谱-质谱（GC-MS）鉴定出主要挥发性化合物为-甲基硫代乙酸酯、甲基硫氰酸盐、二甲基二硫醚、1-癸烯、2-乙基己醇、1,4-十一碳二烯、1-十一烯、1,3-苯并噻唑和 2,5-二甲基吡嗪，1,3-苯并噻唑、2-乙基己醇、甲基硫氰酸盐、二甲基二硫醚和-甲基硫代乙酸酯的抑制率分别为 100%、100%、88.91%、67.64%和 53.29%。-甲基硫代乙酸酯仅在 pH 值为 5.5 时检测到。综上所述，恶臭假单胞菌 CLP-6 产生的 VOCs 在酸性条件下对植物病原菌具有很强的拮抗活性，特别是对青枯雷尔氏菌，可用于开发安全、添加的青枯病防治剂，用于防治烟草和中国南方酸化土壤中其他作物的青枯病。有益细菌产生的 VOCs 穿透根际，抑制植物病原微生物的生长；因此，它们具有作为防治植物病害的生物制剂的潜力。由嗜酸病原菌青枯雷尔氏菌引起的烟草青枯病是中国南方的一种主要细菌性病害，在酸性土壤中普遍存在。本研究发现，恶臭假单胞菌 CLP-6 产生的 VOCs 对重要植物病原菌具有优异的抑制作用。此外，两种 VOC 物质，即 1,3-苯并噻唑和 2-乙基己醇，对青枯雷尔氏菌具有优异的抑制作用，另一种 VOC 物质，即甲基硫氰酸盐，仅在 pH 值为 5.5 时产生。耐酸菌株恶臭假单胞菌 CLP-6 产生的 VOCs 可能具有作为防治中国南方酸化土壤中烟草甚至其他作物青枯病的环保型微生物熏蒸剂的潜力。
