Sugarbeet Research Unit, Edward T. Schaffer Agricultural Research Center, U.S. Department of Agriculture-Agricultural Research Service, Fargo, ND, U.S.A.
Cell & Molecular Sciences, The James Hutton Institute, Dundee, U.K.
Phytopathology. 2024 Oct;114(10):2262-2272. doi: 10.1094/PHYTO-01-24-0034-R. Epub 2024 Oct 7.
Cercospora leaf spot, caused by the fungus Cercospora beticola, is the most destructive foliar disease of sugarbeet worldwide. Resistance to the sterol demethylation inhibitor (DMI) fungicide tetraconazole has been previously correlated with synonymous and nonsynonymous mutations in . Here, we extend these analyses to the DMI fungicides prothioconazole, difenoconazole, and mefentrifluconazole in addition to tetraconazole to confirm whether the synonymous and nonsynonymous mutations at amino acid positions 144 and 170 are associated with resistance to these fungicides. Nearly half of the 593 isolates of collected in the Red River Valley of North Dakota and Minnesota in 2021 were resistant to all four DMIs. Another 20% were resistant to tetraconazole and prothioconazole but sensitive to difenoconazole and mefentrifluconazole. A total of 13% of isolates were sensitive to all DMIs tested. We found five haplotypes and associated them with phenotypes to the four DMIs. The most predominant haplotype (E170_A/L144F_C) correlated with resistance to all four DMIs with up to 97.6% accuracy. The second most common haplotype (E170_A/L144) consisted of isolates associated with resistance phenotypes to tetraconazole and prothioconazole while also exhibiting sensitive phenotypes to difenoconazole and mefentrifluconazole with up to 98.4% accuracy. Quantitative PCR did not identify differences in expression between haplotypes. This study offers an understanding of the importance of codon usage in fungicide resistance and provides crop management acuity for fungicide application decision-making.
尾孢叶斑病由尾孢菌引起，是世界范围内甜菜最具破坏性的叶部病害。对甾醇脱甲基抑制剂（DMI）杀菌剂三唑酮的抗性以前与 中的同义和非同义突变相关。在这里，我们将这些分析扩展到除三唑酮以外的 DMI 杀菌剂丙硫菌唑、咯菌腈和氟环唑，以确认在氨基酸位置 144 和 170 的同义和非同义突变是否与对这些杀菌剂的抗性有关。在 2021 年收集于北达科他州和明尼苏达州红河谷的 593 个 分离株中，近一半对所有四种 DMI 具有抗性。另有 20%的分离株对三唑酮和丙硫菌唑具有抗性，但对咯菌腈和氟环唑敏感。共有 13%的分离株对所有测试的 DMI 敏感。我们发现了 5 个 单倍型，并将它们与四种 DMI 的表型相关联。最主要的单倍型（E170_A/L144F_C）与对所有四种 DMI 的抗性相关，准确率高达 97.6%。第二个最常见的单倍型（E170_A/L144）由与三唑酮和丙硫菌唑抗性表型相关的分离株组成，同时对咯菌腈和氟环唑也表现出敏感表型，准确率高达 98.4%。定量 PCR 未检测到单倍型之间 表达的差异。这项研究提供了对密码子使用在杀菌剂抗性中的重要性的理解，并为杀菌剂应用决策提供了作物管理的敏锐度。
