College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, 430070, China.
Plant Dis. 2021 Feb;105(2):408-415. doi: 10.1094/PDIS-05-20-1128-RE. Epub 2020 Dec 9.
The demethylation inhibitor (DMI) fungicide prochloraz has been widely used in China to control citrus green mold, which is caused by . The 50% effective concentration (EC) values of prochloraz for 129 isolates of collected in 2017 from citrus groves of four provinces of China ranged from 0.0032 to 0.4582 mg/liter. Analysis of the distribution of natural logarithms of EC values indicated that 111 isolates with EC values lower than 0.05 mg/liter could be considered sensitive to prochloraz. Relative baseline sensitivity was established based on the 111 sensitive isolates, and the mean EC value was 0.0090 ± 0.0054 mg/liter (SD). Prochloraz at 60, 100, and 140 mg/liter provided preventive efficacies of 67.8, 93.0, and 96.4%, respectively. Prochloraz at 0.005 and 0.01 mg/liter disrupted cell membrane integrity of conidia but reduced cell membrane permeability of mycelia. Prochloraz at 0.01 mg/liter reduced ergosterol content in mycelia by 41.8%. Two prochloraz-resistant isolates with EC values of 3.97 and 5.68 mg/liter were attained by consecutive subculturing on prochloraz-amended PDA. Studies on the expression levels of three potential target genes, , , and , demonstrated that whether in the absence or presence of prochloraz, only in the resistant isolates was overexpressed at least 10-fold higher than that of the sensitive ones. Sequencing of the three genes showed that only in the resistant isolates had a 199-bp insertion in the promoter region. In addition, only displayed point mutations of G405S, G389C, and Y390S in the coding regions in the resistant isolates. These results were important for understanding the resistance mechanisms of to prochloraz.
脱甲基抑制剂（DMI）杀菌剂百菌清在中国被广泛用于防治由引起的柑橘青霉病。2017 年，从中国四个省份的柑橘园中采集的 129 个分离株的百菌清 50%有效浓度（EC）值范围为 0.0032 至 0.4582 毫克/升。对 EC 值自然对数分布的分析表明，EC 值低于 0.05 毫克/升的 111 个分离株可被认为对百菌清敏感。基于这 111 个敏感分离株建立了相对基线敏感性，平均 EC 值为 0.0090 ± 0.0054 毫克/升（标准差）。百菌清 60、100 和 140 毫克/升的预防效果分别为 67.8%、93.0%和 96.4%。百菌清 0.005 和 0.01 毫克/升破坏了分生孢子的细胞膜完整性，但降低了菌丝的细胞膜通透性。百菌清 0.01 毫克/升使菌丝中的麦角固醇含量降低了 41.8%。通过在添加百菌清的 PDA 上连续传代培养，获得了 EC 值分别为 3.97 和 5.68 毫克/升的两个百菌清抗性分离株。对三个潜在靶基因、、和的表达水平的研究表明，无论是否存在百菌清，抗性分离株中只有至少 10 倍高表达，而敏感分离株中则没有。对这三个基因的测序表明，只有抗性分离株在启动子区域有 199 个碱基对的插入。此外，只有 抗性分离株在编码区显示 G405S、G389C 和 Y390S 的点突变。这些结果对于了解对百菌清的抗性机制很重要。
