文献类型： 外文期刊

作者： Yang, X. J. ¹ ; Yang, L. J. ² ; Zeng, F. S. ² ; Xiang, L. B. ² ; Wang, S. N. ² ; Yu, D. Z. ² ; Ni, H. ¹ ;

作者机构： 1.China Agr Univ, Agron & Biotechnol Coll, Beijing 10094, Peoples R China

2.Hubei Acad Agr Sci, Inst Plant Protect & Soil Sci, Wuhan 430064, Peoples R China

关键词： Data processing;Downy mildew;Ethanol;Plant Data processing;Downy mildew;Ethanol;Plant diseases;Powdery mildew;Risk assessment;natural products;Cucumis sativus;Pseudoperonospora cubensis;Sphaerotheca fuliginea

期刊名称：PLANT DISEASE （ 影响因子：4.438； 五年影响因子：4.7 ）

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收录情况： SCI

摘要： The ethanol extract from rhubarb was commercialized in China (Veguard, Physcion, 5 g/liter AS) for control of cucumber powdery mildew (Sphaerotheca fuliginea) and cucumber downy mildew (Pseudoperonospora cubensis). To provide the basic data for the risk assessment of resistance to this product, physcion was selected to represent the active ingredients to establish baseline sensitivity of powdery mildew and downy mildew populations. For powdery mildew, 262 isolates of S. fuliginea from nine regions and, for downy mildew populations, 116 isolates of P. cubensis from six regions were collected in China during 2004 and 2005 and tested for sensitivity. In addition, the sensitivity of a powdery mildew isolate was monitored for 15 asexual generations under selection pressure with physcion. The results showed that there was no significant difference among regions in the frequency distribution of baseline sensitivity to this ingredient for either cucumber powdery mildew isolates or cucumber downy mildew isolates. Baseline sensitivity was distributed as a normal unimodal curve with a mean median (50%) effective concentration (EC sub(50)) of 0.304 mu g/ml for powdery mildew population and mean EC sub(50) of 0.501 mu g/ml for downy mildew population. The variation of sensitivity to physcion was low because the range factor (maximum EC sub(50)/minimum EC sub(50) of isolates within population) varied from 1.63 to 3.42 among powdery mildew populations and from 1.70 to 2.38 among downy mildew populations. The powdery mildew isolate XZ4 did not decrease sensitivity under the selection pressure of physcion at the dose of EC sub(70) for 15 generations.