【摘要】 采用菌丝生长速率法,对采自广西6个冬瓜和黄瓜产区的116株瓜类疫霉菌进行烯酰吗啉的敏感性检测。结果表明:敏感菌株和中间型菌株分别占测试菌株的8.6%和91.4%,以中间型菌株为优势菌群,所有样区均未检测到抗性菌株;待测菌株的EC50值范围为0.081 3~1.340 0μg/m L,最不敏感菌株是最敏感菌株的16倍,平均EC50值为(0.274 6±0.092 8)μg/m L;116株瓜类疫霉对烯酰吗啉的敏感性分布呈单峰曲线,未出现敏感性下降的亚群体,可将其单峰曲线作为瓜类疫霉对烯酰吗啉的敏感性基线,将烯酰吗啉对该病原群体的平均EC50值作为田间抗药性检测的参考标准。通过室内对敏感菌株进行药剂驯化选育20代,获得抗性指数大于2.0的抗药突变体3株;采用紫外线处理未获得有明显抗性的突变体。3株突变体的部分生物学性状结果表明,突变体对寄主的致病力明显弱于其亲本菌株,突变株DRGL-4和DRYL-154菌株几乎丧失致病力;在不同p H及不同温度培养条件下,部分抗药突变体菌丝生长率与亲本菌株相比均有不同程度的提高。综合分析表明,在当前的管理水平和栽培模式下,瓜类疫霉菌抗药突变体群体在田间难以形成和发展,烯酰吗啉属于低抗性风险的用于防治瓜类疫病的有效杀菌剂。更多还原

【Abstract】 The sensitivity of 116 Phytophthora melonis isolates, which were collected from six wax gourd and cucumber growing areas in Guangxi to dimethomorph was determined by the mycelia growth inhibition method.The results showed that the sensitive, moderate and resistant strains was accounted for 8.6%, 91.4% and 0,respectively. The EC50 values of P. melonis populations ranged from 0.081 3 μg/m L to 1.340 0 μg/m L. EC50 of the most insensitive strain was 16 folds of the most sensitive one, with a mean of( 0.274 6 ±0.092 8)μg/m L. The sensitivity frequency of P. melonis to dimethomorph distributed as unimodal curve, which indicated that there was no resistant subpopulation among these strains, so this sensitivity baseline could be used for resistance monitoring of P. melonis to dimethomorph. Three resistant mutants( resistant factor >2.0) were generated after 20 generations subcultured on dimethomorph-amended medium, but failed to generate resistant mutants by UV-irradiation. Some biological characteristics of resistant mutants were studied in this paper. The results showed that there were significantly differences between the mutants and wild type in pathogenicity, e.g. two of these mutants almost lost their pathogenicity on their host. However, the growth rates of most resistant mutants were greater than that of their parental strains on different p H values and different temperatures. Based on these results, the development of field resistance to dimethomorph in populations of P. melonis is unlikely under the currently employed resistance management strategies, which indicated that the dimethomorph belonged to a low risk fungicide in field application.更多还原