Activity of a novel succinate dehydrogenase inhibitor fungicide pyraziflumid against Sclerotinia sclerotiorum

Pyraziflumid is a novel member of succinate dehydrogenase inhibitor fungicides (SDHI). In this study, baseline sensitivity of Sclerotinia sclerotiorum (Lib.) de Bary to pyraziflumid was determined using 105 strains collected during 2015 and 2017 from different geographical regions in Jiangsu Province of China, and the average EC50 value was 0.0561 (+/- 0.0263) mu g/ml for mycelial growth. There was no cross-resistance between pyraziflumid and the widely used fungicides carbendazim, dimethachlon and the phenylpyrrole fungicide fludioxonil. After pyraziflumid treated, hyphae were contorted with offshoot of top increasing, cell membrane permeability increased markedly, oxalic acid content significantly decreased and mycelial respiration was strongly inhibited. But the number and dry weight of sclerotia did not change significantly. The protective and curative activity test of pyraziflumid suggested that pyraziflumid had great control efficiency against S. sclerotiorum on detached rapeseed leaves, and protective activity was better than curative activity. These results will contribute to us on evaluating the potential of the new SDHI fungicide pyraziflumid for management of diseases caused by S. sclerotiorum and understanding the mode of action of pyraziflumid against S. sclerotiorum.

吡唑氟酰胺是琥珀酸脱氢酶抑制剂类杀菌剂（SDHI）的一种新型成员。在本研究中，利用2015年至2017年期间从中国江苏省不同地理区域采集的105个菌株，测定了核盘菌（Sclerotinia sclerotiorum (Lib.) de Bary）对吡唑氟酰胺的基线敏感性，其菌丝生长的平均EC50值为0.0561（±0.0263）微克/毫升。吡唑氟酰胺与广泛使用的杀菌剂多菌灵、菌核净以及苯基吡咯类杀菌剂咯菌腈之间没有交互抗性。经吡唑氟酰胺处理后，菌丝扭曲，顶端分支增多，细胞膜通透性显著增加，草酸含量明显降低，菌丝呼吸受到强烈抑制，但菌核的数量和干重没有显著变化。吡唑氟酰胺的保护和治疗活性试验表明，吡唑氟酰胺对离体油菜叶片上的核盘菌具有良好的防治效果，且保护活性优于治疗活性。这些结果将有助于我们评估新型SDHI杀菌剂吡唑氟酰胺对核盘菌所致病害的防治潜力，并了解吡唑氟酰胺对核盘菌的作用方式。