基于刃天青微平板法测定交链格孢菌橘致病型对戊唑醇和苯醚甲环唑的敏感性

由交链格孢菌橘致病型(Alternaria alternata tangerine pathotype)引起的柑橘链格孢褐斑病(Alternaria brown spot,ABS)是柑橘上的主要病害，目前主要采用杀菌剂防治。本研究以采自中国各柑橘链格孢褐斑病发生区的54个交链格孢菌橘致病型菌株为供试群体，采用刃天青微平板法测定了病原菌孢子萌发和菌丝生长对戊唑醇和苯醚甲环唑的敏感性。结果表明:刃天青微平板法最佳体系中的培养基为完全培养基(CM)，刃天青终浓度为40 μmol/L，孢子浓度为105个/mL。戊唑醇和苯醚甲环唑的有效抑制中浓度(EC50)范围分别为0.304~0.885 μg/mL和0.367~0.873 μg/mL，平均值分别为0.562和0.609 μg/mL。正态分布检测结果显示:这2种药剂抑制交链格孢菌橘致病型群体的EC50值均符合正态分布，因此认为所得EC50值可作为病原菌对戊唑醇和苯醚甲环唑的敏感性基线。本研究结果可为田间防治褐斑病和监测交链格孢菌对戊唑醇和苯醚甲环唑的抗药性奠定基础。

Sensitivity assay of Alternaria alternata tangerine pathotype from China to tebuconazole and difenoconazole using resazurin-based microtiter

Alternaria brown spot (ABS), caused by Alternaria alternata tangerine pathotype, is one of the main diseases of tangerine, the hybrid of tangerine and grapefruit, and the hybrid of tangerine and orange. Currently, chemical control is the most effective measurement for this disease management. In this study, 54 isolates of A.alternata tangerine pathotype collected from China was selected for the evaluation of EC50 values to two triazole fungicides (tebuconazole and difenoconazole) by using a rapid resazurin-based microtiter assay. The best assay system is as follows:complete medium (CM), 40 μmol/L final concentration of resazurin (RZ), and 105 conidia/mL spore concentration. The EC50 value for tebuconazole and difenoconazole to inhibit the growth of A.alternata tangerine pathotype population ranged from 0.304 to 0.885 μg/mL and from 0.367 to 0.873 μg/mL, respectively, and averaged 0.562 μg/mL and 0.609 μg/mL, respectively. The frequency distributions of EC50 values of 54 isolates to tebuconazole and difenoconazole were unimodal. Therefore, the mean EC50 values could be used as the baseline sensitivities of A.alternata tangerine pathotype population from China. The determination of the baseline sensitivities of A.alternata tangerine pathotype population to these two triazole fungicides laid the foundation for the selection of fungicide in practice of ABS control and for the future monitoring of the development of the fungicide-resistant subpopulation.