【目的】了解华南地区瓜类疫霉(Phytophthora melonis)对甲霜灵的田间抗药性。【方法】2007-2010年从广西、广东两省(区)9个市冬瓜和黄瓜产区采集疫病样品,分离纯化瓜类疫霉,分别采用菌落生长速率法和叶盘漂浮法测定瓜类疫霉对甲霜灵的敏感性,并用药剂驯化方法从敏感性菌株诱导瓜类疫霉抗甲霜灵突变体。【结果】从9个市24个样点共分离纯化获得193株瓜类疫霉,抗药性检测结果表明,敏感菌株、中等抗性菌株和抗性菌株分别占测试菌株的29.0%、18.1%和52.8%;不同地区、不同寄主分离的菌株的抗性频率和抗性水平差异较大,来源于广东的菌株抗性频率和抗性水平一般高于来源广西的菌株,分离自黄瓜的菌株高于分离自冬瓜的菌株,大部分样点抗性菌株占据优势群体,个别菌株的抗性指数高达4226.9,叶盘漂浮法测定结果和菌落生长速率法相似;在含药平板上对敏感菌株进行甲霜灵抗性诱导结果表明,从60%的敏感菌株中成功诱导出对甲霜灵抗性稳定的突变体,突变体的抗性水平为敏感性亲本的189-407倍;9株来源于未施用过甲霜灵等苯基酰胺类杀菌剂样点的菌株均为敏感性菌株,其EC50值为0.0429-0.5461μg/mL,将它们EC50的平均值0.3200±0.1617μg/mL确定为华南地区瓜类疫霉对甲霜灵的敏感性基线;对两个样点的监测结果表明,瓜类疫霉抗甲霜灵菌株的频率及抗性指数有逐年增高趋势。【结论】华南广西和广东两省(区)瓜类疫霉对甲霜灵抗性普遍发生,瓜类疫霉对甲霜灵抗药性产生与其和药剂的接触密切相关。瓜类疫霉敏感性基线的建立,可为今后瓜类疫霉抗甲霜灵的评价和进一步监测提供科学依据。 【Objective】 The objective of this study was to investigate the field resistance of Phytophthora melonis to metalaxyl in southern China. 【Method】 From 2007 to 2010, epidemic samples were collected from winter melons and cucumber producing areas in 9 cities of Guangxi and Guangdong provinces (provinces), and P. melon was separated and purified. The gingivitis was determined by colony growth rate and leaf disc floating method The sensitivity of mold to metalaxyl was also studied. The mutants of melon Phytophthora mevalonella were induced from sensitive strains by using drug domestication method. 【Result】 Ninety-nine P. melitensis strains were isolated and purified from 24 samples in nine cities. The results of drug resistance test showed that the susceptible strains, moderate resistant strains and resistant strains accounted for 29.0% and 18.1% of the tested strains respectively 52.8%. The frequency and level of resistance of isolates isolated from different regions varied greatly. The frequency and resistance level of isolates from Guangdong were generally higher than those from Guangxi. The isolates from cucumber were higher than those from cucumber Most of the isolates isolated from melon belonged to the dominant group, and the resistance index of individual strains was 4226.9. The results of leaf disk floatation method and colony growth rate method were similar. The sensitive strains were treated with ameloblastin The result of inducing resistance showed that mutants resistant to metalaxyl were successfully induced from 60% of the sensitive isolates, and the resistance level of the mutants was 189-407 times of that of the susceptible ones. Nine strains derived from non-application Metalaxyl and other phenylamide fungicide samples of the isolates are sensitive strains, the EC50 value of 0.0429-0.5461μg / mL, the average value of their EC50 0.3200 ± 0.1617μg / mL identified as southern China melons Phytophthora sensitive to metalaxyl Baseline; two samples the results of the monitoring indicate that the anti-Metalaxyl cucurbits Phytophthora resistance index and the frequency has increased year by year. 【Conclusion】 Phytophthora meliloti resistance to metalaxyl generally occurs in Guangxi and Guangdong Provinces of South China. Phytophthora meliloti and metalaxyl resistance are closely related to the drug exposure. The establishment of the baseline of P. meliloti sensitivity could provide a scientific basis for the future evaluation and further monitoring of P. melitensis against metalaxyl.