琥珀酸脱氢酶抑制剂类杀菌剂对禾谷丝核菌的抑制活性及结合模式

Inhibitory activity and binding mode of succinate dehydrogenase inhibitor fungicides against Rhizoctonia cerealis

主要由禾谷丝核菌Rhizoctonia cerealis引起的小麦纹枯病是一种土传真菌病害,自20世纪90年代中期以来,黄淮麦区小麦纹枯病逐渐由次要病害上升为主要病害,对常见的杀菌剂类型已经出现了抗性菌株。新商品化的琥珀酸脱氢酶抑制剂类(SDHIs)杀菌剂对禾谷丝核菌的抑制活性尚未见报道。本研究选取3株禾谷丝核菌ZMDBY-9、JZWZ-8和ZMDBY-6,采用菌丝生长速率法测定了10种SDHIs类杀菌剂萎锈灵、氟酰胺、噻呋酰胺、啶酰菌胺、吡唑萘菌胺、氟唑菌酰胺、苯并烯氟菌唑、氟吡菌酰胺、氟吡菌酰羟胺和联苯吡嗪菌胺对禾谷丝核菌的抑制活性;采用同源模建及分子对接,研究了RcSDH bcd构成的蛋白模型与10种SDHIs类杀菌剂的结合模式,进一步分析了结合能与抑菌效果的关联性。菌丝生长速率法测定结果显示:苯并烯氟菌唑和氟唑菌酰胺对禾谷丝核菌的抑制活性较高,平均有效抑制中浓度(EC50)值小于0.1 mg/L;氟吡菌酰胺与氟唑菌酰羟胺的抑制活性较弱,平均EC50值大于1 mg/L;其他6种杀菌剂的平均EC50值为0.1~0.6 mg/L。分子对接结果显示:在10种SDHIs类杀菌剂中,含吡唑-4-酰胺结构的药剂对禾谷丝核菌的抑制活性最好,结合能更低。其中7种杀菌剂分子的抑制活性与结合能之间存在一定的关联性,表现为抑制活性强结合能往往较低。本文研究结果为SDHIs类杀菌剂在小麦纹枯病化学防治中的应用及基于琥珀酸脱氢酶的药剂设计提供了参考。

Wheat sharp eyespot,mainly caused by Rhizoctonia cerealis,is a soil-borne fungal disease.Since the mid-1990s,it has gradually risen from a minor disease to a major one in the Huang-Huai wheat-growing region.Resistant strains of common fungicides have emerged.The inhibitory activity of newly commercialized succinate dehydrogenase inhibitors(SDHIs)against R.cerealis has not been reported yet.In this study,three strains of R.cerealis(ZMDBY-9,JZWZ-8,and ZMDBY-6)were selected to determine the inhibitory activity of ten SDHIs fungicides including carboxin,flutolanil,thifluzamide,boscalid,isopyrazam,fluxapyroxad,benzovindiflupyr,fluopyram,pydiflumetofen and pyraziflumid,using mycelial growth rate method.Homology modeling and molecular docking were used to investigate the binding modes between RcSDH bcd and these ten SDHIs fungicides as well as analyze the correlation between binding energy and inhibitory effect.The results obtained from the mycelial growth rate method showed that benzovindiflupyr and fluxapyroxad exhibited higher inhibition effects with mean EC50 values less than 0.1 mg/L;while fluopyram and pydiflumetofen displayed weaker inhibitory activities with mean EC50 values greater than 1 mg/L;for the mean EC50 values of other six fungicides ranged from 0.1 to 0.6 mg/L.Molecular docking results indicated that among these ten SDHIs fungicides,those containing pyrazole-4-carboxamide structure possessed better inhibitory activities against R.cerealis and had lower binding energy.There was a certain correlation between the inhibitory activities and binding energies of seven fungicides:fungicides with stronger inhibition often had lower binding energies.The research findings of this study provide references for the application of SDHI fungicides in the chemical control of wheat sharp eyespot and the compound design based on succinate dehydrogenase.