To develop a kind of quaternary ammonium compounds that can safely apply in agriculture for managing the plant bacterial diseases, herein, a series of N-methylmorpholinium derivatives possessing a classical 1,3,4-oxadiazole core were prepared and the antibacterial activities both in vitro and in vivo were screened. Bioassay results revealed that compounds 3l and 3i showed the strongest antibacterial activity toward pathogens Xanthomonas oryzae pv. oryzae and X. axonopodis pv. citri with the lowest EC₅₀ values of 1.40 and 0.90 μg/mL, respectively. Phytotoxicity test trials indicated that target compounds bearing a bulky N-methylmorpholinium pendant are safe for plants. The following in vivo bioassays showed that compound 3l could control the rice bacterial blight disease, thereby affording good control efficiencies of 55.95% (curative activity) and 53.09% (protective activity) at the dose of 200 μg/mL. Preliminary antibacterial mechanism studies suggested that target compounds had strong interactions with the cell membrane of bacteria via scanning electron microscopy imaging. Additionally, this kind of framework also displayed certain antifungal activity toward Fusarium oxysporum and Phytophthora cinnamomi. Given the above privileged characteristics, this kind of 1,3,4-oxadiazole-tailored N-methylmorpholinium derivatives could stimulate the design of safe quaternary ammonium bactericides for controlling plant bacterial diseases.

中文翻译：

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具有 1,3,4-恶二唑核的 N-甲基吗啉衍生物的合成作为可行的抗植物细菌病害的抗菌剂

为开发一种可安全应用于农业防治植物细菌病害的季铵化合物，本文制备了一系列具有经典1,3,4-恶二唑核的N-甲基吗啉衍生物，并在体外具有抗菌活性。并在体内进行了筛选。生物测定结果表明，化合物3l和3i对病原体米黄单胞菌pv显示出最强的抗菌活性。oryzae和X. axonopodis pv。具有最低 EC ₅₀值 1.40 和 0.90  μ 的柑橘克/毫升，分别。植物毒性试验表明，带有庞大的N-甲基吗啉悬垂的目标化合物对植物是安全的。以下体内生物测定表明，化合物3l可以控制水稻白叶枯病，在200 μ g/mL的剂量下具有55.95%（治愈活性）和53.09%（保护活性）的良好控制效率 。初步的抗菌机制研究表明，目标化合物通过扫描电子显微镜成像与细菌细胞膜有很强的相互作用。此外，该类骨架对尖孢镰刀菌和肉桂疫霉也显示出一定的抗真菌活性。. 鉴于上述特权特性，这种1,3,4-恶二唑定制的N-甲基吗啉衍生物可以刺激用于控制植物细菌病害的安全季铵杀菌剂的设计。