Brazil is the biggest producer of sweet oranges and the main exporter of concentrated orange juice in the world. Among the diseases that affect citriculture, Asiatic citrus canker, caused by the bacterial pathogen Xanthomonas citri, represents one of the most significant threats. The current Brazilian legislation regulating the control of citrus canker no longer requires the eradication of affected trees in states where the incidence of the disease is high. Instead, control involves disease control measures, including periodic preventative spraying of copper compounds. The long‐term use of copper for plant disease control has raised concerns about environmental accumulation and toxicity, as well as the selective pressure it exerts leading to the emergence of copper‐resistant X. citri strains. Here, we evaluated hexyl gallate (G6) as an alternative to copper compounds for citrus plant protection. G6 was able to protect citrus nursery trees against X. citri infection. Thirty days after inoculation, the trees treated with G6 developed 0.5 lesions/cm² leaf area compared with the 2.84 lesions/cm² observed in the untreated control trees. Also, G6 did not interfere with germination and root development of tomato, lettuce, and arugula, which is consistent with our previous data showing that G6 is safe for tissue culture cell lines. Membrane permeability tests showed that the primary target of G6 is the bacterial outer membrane. Finally, we could not isolate spontaneous X. citri mutants resistant to G6 nor induce resistance to G6 after long‐term exposures to increasing concentrations of the compound, which suggests that G6 may have multiple cellular targets. This study demonstrated that G6 is a promising candidate for the development and use in citrus canker management.

中文翻译：

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没食子酸己酯用于控制由柠檬黄单胞菌引起的柑橘溃疡病。

巴西是世界上最大的甜橙生产国和浓缩橙汁的主要出口国。在影响柠檬文化的疾病中，由细菌病原体柠檬黄单胞菌引起的亚洲柑橘溃疡病是最重大的威胁之一。巴西现行的管制柑橘溃疡病的立法不再要求在发病率很高的州根除受影响的树木。相反，控制涉及疾病控制措施，包括定期预防性喷洒铜化合物。长期用于植物病害控制的铜引起了人们对环境累积和毒性及其施加的选择性压力的担忧，该选择性压力导致出现了具有铜抗性的柠檬黄单胞菌菌株。这里，我们评估了没食子酸己酯（G6）作为柑橘类植物保护用铜化合物的替代品。G6能够保护柑橘苗圃免受柠檬黄杆菌的感染。接种30天后，用G6处理的树木发展了0.5个病斑/ cm²与2.84病变/厘米相比叶面积²以未处理对照组观察到的树木。另外，G6不会干扰番茄，生菜和芝麻菜的发芽和根部发育，这与我们先前的数据一致，表明G6对于组织培养细胞系是安全的。膜通透性测试表明，G6的主要靶标是细菌外膜。最后，在长期暴露于浓度不断增加的化合物后，我们无法分离出对G6有抗性的自发柠檬酸X.突变体，也无法诱导对G6的抗性，这表明G6可能具有多个细胞靶标。这项研究表明，G6是柑桔溃疡病管理中开发和使用的有希望的候选者。