Abstract：
Rice blast, caused by Magnaporthe oryzae, is a devastating fungal disease worldwide. Pydiflumetofen (Pyd) is a new succinate dehydrogenase inhibitor (SDHI) that exhibited anti-fungal activity against M. oryzae. However, control of rice blast by Pyd and risk of resistance to Pyd are not well studied in this pathogen. The baseline sensitivity of 109 M. oryzae strains to Pyd was determined using mycelial growth rate assay, with EC50 values ranging from 0.291 to 2.1313 μg/mL, and an average EC50 value of 1.1005 ± 0.3727 μg/mL. Totally 28 Pyd-resistant (PydR) mutants with 15 genotypes of point mutations in succinate dehydrogenase (SDH) complex were obtained, and the resistance level could be divided into three categories of very high resistance (VHR), high resistance (HR) and moderate resistance (MR) with the resistance factors (RFs) of >1000, 105.74-986.13 and 81.92-99.48, respectively. Molecular docking revealed that all 15 mutations decreased the binding-force score for the affinity between Pyd and target subunits, which further confirmed that these 15 genotypes of point mutations were responsible for the resistance to Pyd in M. oryzae. There was positive cross resistance between Pyd and other SDHIs, such as fluxapyroxad, penflufen or carboxin, while there was no cross-resistance between Pyd and carbendazim, prochloraz or azoxystrobin in M. oryzae, however, PydR mutants with SdhBP198Q, SdhCL66F or SdhCL66R genotype were still sensitive to the other 3 SDHIs, indicating lack of cross resistance. The results of fitness study revealed that the point mutations in MoSdhB/C/D genes might reduce the hyphae growth and sporulation, but could improve the pathogenicity in M. oryzae. Taken together, the risk of resistance to Pyd might be moderate to high, and it should be used as tank-mixtures with other classes of fungicides to delay resistance development when it is used for the control of rice blast in the field.
摘要：
稻瘟病,由稻瘟病引起的，是全球范围内毁灭性的真菌病。吡氟美芬（Pyd）是一种新型的琥珀酸脱氢酶抑制剂（SDHI），对米曲霉具有抗真菌活性。然而,在该病原体中，尚未很好地研究Pyd对稻瘟病的控制和对Pyd的抗性风险。109株米曲霉菌株对Pyd的基线敏感性使用菌丝生长速率测定，EC50值范围为0.291至2.1313μg/mL，平均EC50值为1.1005±0.3727μg/mL。在琥珀酸脱氢酶（SDH）复合物中获得了28个Pyd抗性（PydR）突变体，具有15个基因型的点突变，阻力水平可分为三类极高阻力(VHR)，高抗性（HR）和中等抗性（MR），抗性因子（RF）分别为>1000，105.74-986.13和81.92-99.48。分子对接显示，所有15个突变都降低了Pyd和靶亚基之间亲和力的结合力得分，这进一步证实了这15种点突变基因型是米曲霉对Pyd的抗性的原因。Pyd和其他SDHIs之间存在正交叉抗性，比如fluxapyroxad，penflufen或羧基，虽然Pyd和多菌灵之间没有交叉抗性，米曲霉中的丙草胺或唑菌酯，然而,具有SdhBP198Q的PydR突变体,SdhCL66F或SdhCL66R基因型对其他3种SDHI仍然敏感，表明缺乏交叉抗性。适应性研究结果表明，MoSdhB/C/D基因的点突变可能会降低菌丝生长和孢子形成，但可以提高米曲霉的致病性。一起来看,抵抗Pyd的风险可能是中等到高，当用于控制稻瘟病时，应与其他类型的杀菌剂一起用作罐混合物，以延迟抗性的发展。
