College of Plant Science and Technology, Huazhong Agricultural University, Wuhan 430070, China.
College of Plant Science and Technology, Huazhong Agricultural University, Wuhan 430070, China.
Pestic Biochem Physiol. 2021 Feb;172:104752. doi: 10.1016/j.pestbp.2020.104752. Epub 2020 Nov 19.
Green mold, caused by Penicillium digitatum, is the most important citrus postharvest disease worldwide and often causes substantial economic losses to the citrus industry. The demethylation inhibitor (DMI) fungicides are highly effective against a broad range of fungal pathogens, but the DMI fungicide propiconazole has not been registered yet in China for the control of citrus green mold. In this study, baseline sensitivity of P. digitatum to propiconazole was determined. The frequency distribution of logarithms of EC values for 118 isolates collected from five regions in China was bimodal, and among the 118 isolates, 18 isolates were less sensitive or had low resistance to propiconazole. The mean EC value of the sensitive 100 isolates was 0.104 mg/L. Preventive control efficacies on Satsuma mandarin for propiconazole at 200 and 400 mg/L were 63.1 and 84.3%, respectively. The fruit treated with propiconazole at 40 and 100 mg/L produced significantly fewer conidia, and the virulence of the conidia decreased by 12.3 and 14.8%, respectively. Studies with propidium iodide showed that the membrane integrity was damaged for 25.6% of conidia produced on PDA amended with propiconazole at 0.1 mg/L. Fluorescence microscopy observations of P. digitatum conidia stained with 2,7-dichlorofluorescin showed that propiconazole significantly induced the generation of intracellular reactive oxygen species (ROS). Compared with the sensitive isolates, no point mutations were detected in either the coding or promoter region of the target gene CYP51A of the isolates with low resistance to propiconazole. However, the relative expression levels of CYP51A for three resistant isolates were higher than sensitive isolates, and the mean relative expression was 2.08 for resistant isolates versus 0.62 for sensitive isolates in the absence of propiconazole and 3.12 versus 1.44 in the presence of propiconazole. These results indicate increased expression of CYP51A is the molecular mechanism for low resistance of P. digitatum to propiconazole.
绿霉病由指状青霉引起，是全球最重要的柑橘采后病害，常给柑橘产业造成巨大经济损失。脱甲基抑制剂（DMI）类杀菌剂对广泛的真菌病原体具有高度有效性，但 DMI 类杀菌剂丙环唑尚未在中国登记用于防治柑橘绿霉病。本研究测定了指状青霉对丙环唑的基础敏感性。从中国五个地区采集的 118 个分离株的 EC 值对数的频率分布呈双峰型，其中 18 个分离株对丙环唑的敏感性较低或具有低抗性。100 个敏感分离株的平均 EC 值为 0.104mg/L。200 和 400mg/L 丙环唑对温州蜜柑的预防性防治效果分别为 63.1%和 84.3%。用丙环唑处理 40 和 100mg/L 的果实产生的分生孢子明显减少，分生孢子的毒力分别降低了 12.3%和 14.8%。碘化丙啶研究表明，在添加 0.1mg/L 丙环唑的 PDA 上产生的 25.6%的分生孢子的膜完整性受到破坏。用 2,7-二氯荧光素染色观察指状青霉分生孢子的荧光显微镜观察表明，丙环唑显著诱导了细胞内活性氧（ROS）的产生。与敏感分离株相比，低抗丙环唑分离株的靶基因 CYP51A 的编码区或启动子区未检测到点突变。然而，与敏感分离株相比，三个抗性分离株的 CYP51A 的相对表达水平较高，在没有丙环唑的情况下，抗性分离株的平均相对表达为 2.08，而敏感分离株为 0.62；在有丙环唑的情况下，抗性分离株为 3.12，而敏感分离株为 1.44。这些结果表明 CYP51A 的高表达是指状青霉对丙环唑低抗性的分子机制。
