疫霉菌对霜脲氰抗性遗传及对霜脲氰和甲霜灵的交互抗性

就疫霉菌对霜脲氰抗性的产生和遗传，以及疫霉菌对霜脲氰和甲霜灵的交互抗性进行了研究。结果表明，苎麻疫霉容易对霜脲氰产生抗药性突变，但抗性在连续３代单游动孢子分离过程中逐渐丧失。大雄疫霉对霜脲氰不易产生抗性突变，恶疫霉、大雄疫霉和苎麻疫霉对甲霜灵和霜脲氰不存在交互抗性     

Sensitivity of European Plasmopara viticola populations to cymoxanil

Between 1995 and 1997, 278 grape downy mildew (Plasmopara viticola) populations originating from European vineyards were characterised for their sensitivity to cymoxanil in a leaf-disc assay. The sensitivity profile revealed a wide distribution, with minimum inhibitory concentrations (MIC) ranging from 10 to more than 800 mg litre⁻¹. EC₅₀ values ranged from 1 to more than 800 mg litre⁻¹ with an average of 125 mg litre⁻¹. The sensitivity distribution was stable between 1995 and 1997. Surprisingly, populations from Portugal appeared significantly more sensitive than those from France or Italy, which could not be linked to differential cymoxanil usage in these countries. P viticola populations collected outside Europe and never exposed to cymoxanil appeared significantly more sensitive than exposed European populations, with an average EC₅₀ value of 10 mg litre⁻¹. The level of sensitivity of European P viticola populations was relatively unaffected by the number of cymoxanil applications made during a season or by the number of years of cymoxanil use. No link was found between the level of sensitivity in the leaf-disc assay and the level of performance of the cymoxanil mixtures used in the fields where the populations originated. Specific field trials conducted in Italy and Portugal have shown that the performance of cymoxanil-based mixtures remained good even on populations of the grape downy mildew fungus characterised as less sensitive in the leaf-disc assay. While there are no baseline sensitivity data for pre-commercialisation P viticola populations, the results of our study suggest that a shift in sensitivity (12.5-fold) may have occurred in some areas since introduction of cymoxanil on grapes nearly 20 years ago. Because cymoxanil is never used alone, it is difficult to determine whether or not practical resistance is occurring in European vineyards. © 1999 Society of Chemical Industry     

江西省辣椒疫霉病菌的交配型及对霜脲氰敏感性的测定

由辣椒疫霉病菌Phytophthora capsici引起的辣椒疫病是辣椒生产上一种重要病害,在我国各地均有发生.辣椒疫霉是一种异宗配合的卵菌.异宗配合的疫霉菌的不同交配型菌株成对培养时,可以形成有性器官并发生基因重组,使该种病菌获得更强的生存能力、致病力和更广泛的寄主范围.因此,研究疫霉交配型在理论和实践上均具有重要意义.霜脲氰(cymoxanil)由美国杜邦公司开发,用于卵菌纲病害的防治.自投入市场使用,至今未发现在自然条件下关于疫霉菌对霜脲氰抗药性报道.     

霜脲氰和代森锰锌对马铃薯晚疫病菌的离体活性及混合增效作用

测定霜脲氰、代森锰锌对马铃薯晚疫病菌不同生长发育阶段的毒力,发现霜脲氰抑制马铃薯晚疫病菌菌丝生长的活性明显高于代森锰锌,抑制孢子囊和游动孢子萌发及孢子囊释放游动孢子的活性明显低于代森锰锌;两药抑制游动孢子游动的活性很低。以1∶7、1∶8混配对游动孢子萌发及菌丝生长的抑制表现增效,以1∶1~1∶10混配对抑制孢子囊萌发的增效系数为1.55~5.39,其中1∶5的增效系数高达5.39。     

Sensitivities of Phytophthora infestans to Metalaxyl, Cymoxanil, and Dimethomorph

The isolates of Phytophthora infestans on tomato in the Guangxi Zhuang Autonomous Region, China, were determined for the sensitivities to metalaxyl, cymoxanil and dimethomorph to give the basic information for integrating disease management. Sensitivities were tested by measuring the radial growth on agar medium amended with fungicide, compared with the floating-leaf-disk method. 239 isolates were collected from eight tomato growing areas during 2000-2006. The testing results indicated that the frequencies of sensitive, intermediate, and resistant isolates to metalaxyl were 42.26, 35.98, and 23.53%, respectively. Variations in sensitivities amongst isolates from different areas or different years were very high for metalaxyl. All isolates from Tianlin and Wuxuan were sensitive to metalaxyl, but the metalaxyl-resistant isolates predominated in Tianyang, with the frequency of 51.35%. The EC50 values of certain isolates from Tianyang were higher than 500 μg·mL^-1 and their resistance levels were over 100 000 folds. Cymoxanil has been used for nearly 10 years in Guangxi, and dimethomorph has been used for 5-6 years. However, there was no decrease in sensitivity of P. infestans populations and the sensitivities of the pathogen were nearly normally distributed. Hence, their mean ECs0 value [cymoxanil （0.1647 ±0.0255） μg·mL^-1, dimethomorph （0.0970 ± 0.0052） μg·mL^-1 could be used as the baseline sensitivities for monitoring the field resistance development. The comparison with the floating-leaf-disk method indicates that both the techniques provided equivalent results. These studies suggested that metalaxyl can be continuously applied in Tianlin, Wuxuan, and Nanning due to the resistant isolates that have not been found, while for those areas with resistant isolate, the use of metalaxyl should be reduced or alternated, and cymoxanil or dimethomorph was recommended for controlling late blight disease of tomato.     

Metabolism of fungicidal cyanooximes, cymoxanil and analogues in various strains of Botrytis cinerea

BACKGROUND: The metabolism of cymoxanil [1‐(2‐cyano‐2‐methoxyiminoacetyl)‐3‐ethylurea] and fungicidal cyanooxime analogues was monitored on three phenotypes of Botrytis cinerea Pers. ex Fr. differing in their sensitivity towards cymoxanil. For this purpose, labelled [2‐¹⁴C]cymoxanil was added either to the culture medium of these strains or to its cell‐free extract. RESULTS: In the culture medium of the most sensitive strain, four main metabolites were detected. Three were isolated and identified. Cymoxanil was quickly metabolised by at least three concurrent enzymatic pathways: (i) cyclisation leading, after hydrolysis, to ethylparabanic acid, (ii) reduction giving demethoxylated cymoxanil, (iii) hydrolysis followed by reduction and then acetylation leading to N‐acetylcyanoglycine. In the cell‐free extract of the same strain, only the first and the second of these enzymatic reactions occurred. By comparing the metabolic profile of the most sensitive strain with that of the less sensitive ones, it was shown that the decrease in sensitivity to cymoxanil correlates with a reduced acetylcyanoglycine formation. Among all metabolites, only N‐acetylcyanoglycine is active against the most sensitive strain. Moreover, in a culture of this strain, two other fungicidal cyanooximes were also metabolised into this metabolite. CONCLUSION: The formation of N‐acetylcyanoglycine may play an important role in the fungitoxicity of cymoxanil and cyanooxime derivatives. Copyright © 2008 Society of Chemical Industry     

复配剂中霜脲氰在马铃薯和土壤中残留动态研究

采用田间试验方法,研究了霜脲氰在马铃薯及土壤中的残留动态,应用液相色谱法测定了霜脲氰在马铃薯和土壤中的残留量。结果表明,霜脲氰在马铃薯和土壤中消解较快,半衰期分别为2．26d和5．75d,施药3240g ai·hm^-23次时,末次施药距收获间隔28d,霜脲氰的残留量在马铃薯中低于0．0098mg·kg^-1,在土壤中为ND-0．0100mg·kg^-1。该药属易分解农药（％〈30d）,按推荐使用剂量使用是安全的。     

葡萄和土壤中霜脲氰的残留分析方法

为了评价霜脲氰的环境安全性,指导含霜脲氰类农药的科学合理使用,建立了霜脲氰在葡萄及其土壤中的残留分析方法.葡萄和土壤样品分别用丙酮和乙酸乙酯提取,经弗罗里硅土柱净化,高效液相色谱(HPLC)测定,霜脲氰的最小检测量为3.0×10-10 g,在葡萄和土壤中的最低检出限为1.5×10-3和3.0×10-3 mg/kg.当添加水平为0.05～1.0 mg/kg时,霜脲氰在土壤中的平均回收率为83.32%～104.22%,变异系数为5.34%～6.11%;在葡萄样品中的平均回收率为80.85%～98.84%,变异系数为3.30%～7.69%.     

马铃薯晚疫病菌对瑞毒霉与霜脲氰的交互抗性

2008~2011年在黑龙江省共分离了41个马铃薯晚疫病菌,并测定了这些菌株对瑞毒霉和霜脲氰的敏感性和交互抗性。瑞毒霉测定结果显示6个(14.63%)菌株显示为敏感性,11个(26.83%)菌株显示为中抗,24个(58.54%)菌株显示为抗性。这说明黑龙江省分离的晚疫病菌已对瑞毒霉产生抗性。对于霜脲氰,EC50值为0.0630~2.1289μg/mL,最不敏感菌株是最敏感菌株的33.79倍,敏感性基线值为0.1879μg/mL。交互抗性分析结果显示,未产生交互抗性的菌株为73.16%,产生交互抗性菌株为26.84%。以上结果说明霜脲氰和瑞毒霉不能交叉使用。     

Systemicity and persistence of cymoxanil in mixture with oxadixyl and mancozeb against Phytophthora infestans and Plasmopara viticola

Uptake and translocation of the fungicide cymoxanil was studied using tomato and potato plants infected with Phytophthora infestans and grape plants infected with Plasmopara viticola. Translocation of cymoxanil was mainly translaminar and acropetal from roots and stems to leaves to an extent similar to that of the phenylamide fungicide oxadixyl. Basipetal translocation from upper to lower leaves, as well as lateral movement, was also observed but to a lesser extent. Plant parts that grew after application were protected against P. infestans and P. viticola because of systemic activity up to 7 days by cymoxanil alone and up to 14 days when cymoxanil was used as part of a three-way mixture with oxadixyl and mancozeb. Drench application of cymoxanil and a simultaneous spray application of mancozeb against P. infestans and P. viticola resulted in a significant synergistic interaction. The spray application of the three-way mixture oxadixyl/mancozeb/cymoxanil was more effective against both sensitive and phenylamide-resistant strains of P. infestans and P. viticola than the individual components alone, representing significant levels of synergistic interactions. Synergy ratios were higher for resistant than for sensitive strains of both pathogens.