Li Bin, Zheng Zhitian, Liu Xiumei, Cai Yiqiang, Mao Xuewei, Zhou Mingguo
College of Plant Protection, Nanjing Agricultural University, Key Laboratory of Pesticide, Nanjing, Jiangsu Province, 210095, China.
Plant Dis. 2016 Aug;100(8):1754-1761. doi: 10.1094/PDIS-02-16-0169-RE. Epub 2016 Jun 8.
Fusarium asiaticum is a critical pathogen of Fusarium head blight (FHB) in the southern part of China. The fungicide phenamacril has been extensively used for controlling FHB in recent years, which reduced both FHB severity and mycotoxin production. Our previous report indicated that resistance of F. asiaticum to phenamacril was related to mutations in myosin5. A recent article revealed that the resistance level of phenamacril-resistant mutants was associated with the genotypes of myosin5 in these mutants. In total, we obtained 239 resistant isolates by fungicide domestication, and 82 resistant mutants were randomly selected for further study. Of these mutants, 25.6, 7.3, and 67.1% showed low resistance (LR), moderate resistance (MR), and high resistance (HR), respectively, to phenamacril determined by 50% effective concentration values. Point mutations A135T, V151M, P204S, I434M, A577T, R580G/H, or I581F led to LR. Point mutations S418R, I424R, and A577G were responsible for MR and point mutations K216R/E, S217P/L, or E420K/G/D conferred HR. Interestingly, all of the mutations concentrated in the myosin5 motor domain and mutations conferring HR occurred at codon 217 and 420, which we called the core region. Homology modeling revealed that mutations far from the core region led to a lower resistance degree. Phenotype assays revealed that the most highly resistant mutants did not significantly change pathogenicity but decreased conidia production compared with the wild type, which may slow down the formation of the resistant pathogen population in the fields.
亚洲镰刀菌是中国南方小麦赤霉病的关键病原菌。近年来，杀菌剂苯醚甲环唑已被广泛用于防治小麦赤霉病，它既能降低赤霉病的严重程度，又能减少霉菌毒素的产生。我们之前的报告表明，亚洲镰刀菌对苯醚甲环唑的抗性与肌球蛋白5的突变有关。最近的一篇文章显示，苯醚甲环唑抗性突变体的抗性水平与这些突变体中肌球蛋白5的基因型有关。我们通过杀菌剂驯化共获得了239个抗性分离株，并随机选择了82个抗性突变体进行进一步研究。在这些突变体中，根据50%有效浓度值测定，分别有25.6%、7.3%和67.1%对苯醚甲环唑表现出低抗性（LR）、中抗性（MR）和高抗性（HR）。点突变A135T、V151M、P204S、I434M、A577T、R580G/H或I581F导致低抗性。点突变S418R、I424R和A577G导致中抗性，点突变K216R/E、S217P/L或E420K/G/D赋予高抗性。有趣的是，所有突变都集中在肌球蛋白5的运动结构域，赋予高抗性的突变发生在密码子217和420处，我们将其称为核心区域。同源建模显示，远离核心区域的突变导致较低的抗性程度。表型分析表明，与野生型相比，抗性最强的突变体致病性没有显著变化，但分生孢子产量降低，这可能会减缓田间抗性病原菌群体的形成。
