Pasche J S, Piche L M, Gudmestad N C
Department of Plant Pathology, North Dakota State University, Fargo 58105.
Plant Dis. 2005 Mar;89(3):269-278. doi: 10.1094/PD-89-0269.
Isolates of Alternaria solani previously collected from throughout the Midwestern United States and characterized as being azoxystrobin sensitive or reduced sensitive were tested for sensitivity to the Quinone outside inhibitor (QI) fungicides famoxadone and fenamidone and the carboxamide fungicide boscalid. All three fungicides affect mitochondrial respiration: famoxadone and fenamidone at complex III, and boscalid at complex II. A. solani isolates possessing reducedsensitivity to azoxystrobin also were less sensitive in vitro to famoxadone and fenamidone compared with azoxystrobin-sensitive isolates, but the shift in sensitivity was of lower magnitude, approximately 2- to 3-fold versus approximately 12-fold for azoxystrobin. The in vitro EC values, the concentration that effectively reduces germination by 50% relative to the untreated control, for sensitive A. solani isolates were significantly lower for famoxadone and azoxystrobin than for fenamidone and boscalid; whereas, for reduced-sensitive isolates, famoxadone EC values were significantly lower than all other fungicides. Isolates of A. solani with reducedsensitivity to azoxystrobin were twofold more sensitive in vitro to boscalid than were azoxystrobin-sensitive wild-type isolates, displaying negative cross-sensitivity. All isolates determined to have reduced-sensitivity to azoxystrobin also were determined to possess the amino acid substitution of phenylalanine with leucine at position 129 (F129L mutation) using real-time polymerase chain reaction. In vivo studies were performed to determine the effects of in vitro sensitivity shifts on early blight disease control provided by each fungicide over a range of concentrations. Reduced-sensitivity to azoxystrobin did not significantly affect disease control provided by famoxadone, regardless of the wide range of in vitro famoxadone EC values. Efficacy of fenamidone was affected by some azoxystrobin reduced-sensitive A. solani isolates, but not others. Boscalid controlled azoxystrobin-sensitive and reduced-sensitive isolates with equal effectiveness. These results suggest that the F129L mutation present in A. solani does not convey cross-sensitivity in vivo among all QI or related fungicides, and that two- to threefold shifts in in vitro sensitivity among A. solani isolates does not appreciably affect disease control.
对先前从美国中西部各地收集的、被鉴定为对嘧菌酯敏感或敏感性降低的链格孢菌分离株，进行了对醌外抑制剂（QI）类杀菌剂恶唑菌酮和苯氧菌胺以及甲酰胺类杀菌剂啶酰菌胺的敏感性测试。这三种杀菌剂均影响线粒体呼吸作用：恶唑菌酮和苯氧菌胺作用于复合体III，啶酰菌胺作用于复合体II。与对嘧菌酯敏感的分离株相比，对嘧菌酯敏感性降低的链格孢菌分离株在体外对恶唑菌酮和苯氧菌胺的敏感性也较低，但敏感性变化幅度较小，约为2至3倍，而嘧菌酯的变化幅度约为12倍。对于敏感的链格孢菌分离株，恶唑菌酮和嘧菌酯的体外有效浓度（相对于未处理对照有效降低发芽率50%的浓度）显著低于苯氧菌胺和啶酰菌胺；而对于敏感性降低的分离株，恶唑菌酮的有效浓度显著低于所有其他杀菌剂。对嘧菌酯敏感性降低的链格孢菌分离株在体外对啶酰菌胺的敏感性比对嘧菌酯敏感的野生型分离株高两倍，表现出负交互敏感性。使用实时聚合酶链反应确定，所有被判定对嘧菌酯敏感性降低的分离株在第129位均具有苯丙氨酸被亮氨酸取代的氨基酸替换（F129L突变）。进行了体内研究，以确定体外敏感性变化对每种杀菌剂在一系列浓度下对早疫病防治效果的影响。无论体外恶唑菌酮有效浓度范围如何，对嘧菌酯敏感性降低对恶唑菌酮的病害防治效果均无显著影响。部分对嘧菌酯敏感性降低的链格孢菌分离株影响了苯氧菌胺的防治效果，但其他分离株未受影响。啶酰菌胺对嘧菌酯敏感和敏感性降低的分离株防治效果相同。这些结果表明，链格孢菌中存在的F129L突变在体内并非对所有QI类或相关杀菌剂均表现出交互敏感性，链格孢菌分离株之间体外敏感性2至3倍的变化对病害防治效果并无明显影响。
