番茄晚疫病菌对甲霜灵、霜脲氰和烯酰吗啉的敏感性检测

 【目的】研究广西番茄晚疫病菌对甲霜灵、霜脲氰和烯酰吗啉的敏感性，以期为该病的综合治理提供科学依据。【方法】用菌落生长直径法测定病菌对甲霜灵、霜脲氰和烯酰吗啉的敏感性，并用叶盘漂浮法加以比较。【结果】2000～2006年，从广西8个冬春植番茄区采集分离了239个菌株，测定结果表明，对甲霜灵表现为敏感型、中间型和抗性型的频率分别为42.26%、35.98%和23.53%，不同地区和年份的菌株对甲霜灵的敏感性差异很大。来自田林县、武宣县的菌株均为甲霜灵敏感性菌株，但在田阳县，抗甲霜灵菌株占优势，抗性频率高达51.35%，一些菌株的EC50值在500 µg•ml-1以上，抗性水平超过105倍。虽然霜脲氰在广西使用了近10年，烯酰吗啉也已应用了5～6年，但并未检测到番茄晚疫病菌对它们的敏感性下降的抗药性亚群体，病菌的敏感性接近正态分布，因此可以采用它们的平均EC50值（霜脲氰0.1647±0.0255 µg•ml-1，烯酰吗啉0.0970±0.0052 µg•ml-1）作为抗药性监测的敏感性基线。叶盘漂浮法测定结果与菌落生长直径法一致。【结论】广西田林县、武宣县和南宁市番茄晚疫病菌尚未出现抗甲霜灵菌株，仍可用甲霜灵来防治该病，而其它地区则应减少或不使用甲霜灵，改用霜脲氰或烯酰吗啉。

Sensitivities of Phytophthora infestans to Metalaxyl,Cymoxanil,and Dimethomorph

【Objective】Isolates of Phytophthora infestans on tomato in Guangxi province were determined for the sensitivities to metalaxyl, cymoxanil and dimethomorph in order to give the basic information for integrate management of this disease.【Method】Sensitivities were determined by measuring radial growth on agar medium amended with fungicide, compared with the floating-leaf-disk method. 【Result】 Two hundred and thirty-nine isolates were collected from eight tomato growing areas during 2000 to 2006. The results of determine showed that the frequencies of sensitive, intermediate and resistant isolates to metalaxyl were 42.26%, 35.98% and 23.53%, respectively, while the frequencies of sensitive, intermediate isolates to cymoxanil were 37.24% and 62.76%, respectively, and that to dimethomorph were 54.81% and 45.19%, respectively. However, no isolate resistant either to cymoxanil or to dimethomorph was detected. The baselines of sensitivity to metalaxyl, cymoxanil, and dimethomorph were 0.003599µg/ml, 0.07156µg/ml and 0.0627µg/ml, respectively. Variations in sensitivities among isolates from different areas or different years were low for cymoxanil and dimethomorph, but very high for metalaxyl. All isolates from Tianlin and Wuxuan were sensitive to metalaxyl. But metalaxyl-resistant isolates predominated in Tianyang, with the frequency of 51.35%. The EC50 values of some isolates from Tianyang were higher than 500µg/ml and their resistance levels were over 100000 folds. The comparison with the floating-leaf-disk method indicated both techniques provided equivalent results.【Conclusion】 These studies suggested that metalaxyl could still be used in Tianlin, Wuxuan and Nanning, where the resistant isolates had not been found, but in other areas, the use of metalaxyl should be reduced or stopped, and cymoxanil or dimethomorph was recommended.