致病疫霉对缬菌胺抗性突变体生物学特性及抗性风险量化评估

 通过研究致病疫霉对缬菌胺抗性突变体的生物学特性,评估致病疫霉对缬菌胺产生抗性的风险。采用菌丝生长速率法检测田间菌株对缬菌胺的敏感性;通过比较抗性突变体在无药条件下继代培养前后对缬菌胺的敏感性来确定其抗性稳定性;采用离体叶片法测定抗性突变体及其亲本敏感菌株的适合度和竞争力;通过量化7个基本抗性因素的风险值评估致病疫霉对缬菌胺的基本抗性风险。结果表明:在2018年从内蒙、河北、贵州、四川、黑龙江等五省(自治区)采集分离的153个菌株和2019年从河北、内蒙采集分离的40个菌株中低抗菌株分别占31.4%和35.0%,敏感菌株分别占68.6%和65.0%,抗性指数均为0.34,抗性倍数分别为1.5和2.1,未发现中抗和高抗菌株;8个抗性突变体在无药条件下继代培养10代后,少数抗性突变体的抗药性不能稳定遗传;6个抗性突变体的适合度均显著低于其亲本敏感菌株;4个抗性突变体与其亲本菌株的孢子囊不同比率混合物分别在离体叶片上继代培养1、3、7代的抗性频率显著低于初始抗性频率或与初始抗性频率无显著差异;致病疫霉对缬菌胺7个基本抗性因素的风险值之和为9,推测致病疫霉对缬菌胺的基本抗性风险为低至中等。建议加强致病疫霉菌群体对缬菌胺的抗性监测,将缬菌胺与不同作用机理的杀菌剂交替或混合使用,以延缓抗药性产生和发展。

Biological characteristics and quantitative assessment of resistance risk in valifenalate-resistant mutants of Phytophthora infestans

The biological characteristics of valifenalate-resistant mutants of Phytophthora infestans were studied for risk evaluation of resistance to valifenalate. Sensitivities to valifenalate of field isolates were detected through mycelial growth rate test. The resistance stability of the resistant mutants was determined through comparing the sensitivity to valifenalate of the resistant mutants before subculturing in the absence of valifenalate with the sensitivity to valifenalate of the resistant mutants after subculturing in the absence of valifenalate. The fitness and the competitiveness of six resistant mutants with their parent sensitive strains were determined on detached leaves. The inherent risk of resistance of P. infestans to valifenalate was evaluated through accumulation of risks of se-ven influence factors. The results showed that lowly-resistant isolates accounted for 31.4% and 35.0%,sensitive isolates accounted for 68.6% and 65.0%,resistance index was 0.34, resistance factors were 1.5 and 2.1, no moderately-resistant isolates and highly-resistant isolates were detected among 153 isolates collected and isolated in 2018 from Inner Mongolia, Hebei, Guizhou, Sichuan and Heilongjiang and 40 isolates collected and isolated in 2019 from Hebei and Inner Mongolia. Resistance of few resistant mutants could not be inherited stably after eight resistant mutants were subcultured for ten generations in the absence of valifenalate. The fitness of eight resistant mutants was significantly lower than that of their parent sensitive strains. The resistance frequencies in the sporangial mixtures of the four resistant mutants with their parent strains were significantly lower than or not significantly different from the initial resistance frequencies after the sporangial mixtures of the four resistant mutants with their parent strains at different ratios were subcultured for one, three and seven generations on detached leaves of potato, respectively. The inherent risk values of seven factors influencing resistance to valifenalate in P. infestans were accumulated to 9, hence, it was speculated that the inherent resistance risk of P. infestans to valifenalate could be low to moderate. It is necessary to strengthen monitoring of resistance of P. infestans to valifenalate, and use valifenalate in alternation or mixture with the fungicides of different action modes to delay the buildup and development of resistance to valifenalate.