苹果斑点落叶病菌对戊唑醇敏感基线建立及抗性突变体适合度

本研究测定了苹果斑点落叶病菌对戊唑醇的敏感性,并建立了敏感基线;在此基础上,室内筛选获得了9株抗戊唑醇突变体,对其适合度进行了测定,为指导戊唑醇防治苹果斑点落叶病提供理论依据。在山西省5个地市未使用过戊唑醇及同类药剂的果园中采集分离得到64株苹果斑点落叶病菌,敏感性测定结果表明,其EC50值在0.768 7~2.673 8μg·mL~(-1)之间,平均值为1.622 4±0.558 2μg·mL~(-1),呈连续性单峰曲线,可作为苹果斑点落叶病菌对戊唑醇的相对敏感基线。通过紫外线(UV)诱导获得低抗突变体6株,药剂驯化获得中抗突变体3株。2株中抗突变体抗药性可稳定遗传;低抗突变体在无药剂胁迫时,药剂敏感性上升。抗性突变体适合度测定结果显示,突变体菌丝生长速率、产孢量、孢子萌发率及分生孢子竞争力均低于敏感菌株。突变体在无药情况下致病力比敏感菌株弱。

Baseline sensitivity of Alternaria alternata f. sp. mali to tebuconazole and fitness of resistant mutants

The sensitivity of Alternaria alternata f. sp. mali to tebuconazole was tested and the baseline sensiti-vity was subsequently established. On this basis, the tebuconazole-resistant mutants of the pathogen were induced in lab. Fitness of the mutants was studied to provide theoretical guides for the rational use of tebuconazole in control of A. alternata f. sp. mali. Sixty-four isolates of A. alternata f. sp. mali from five cities of Shanxi province, where tebuconazole and other DMI fungicides had not been used, were isolated and the sensitivity of the isolates to tebuconazole was determined. The sensitivity of the 64 isolates appeared as a single peak curve. The EC₅₀ values of these isolates ranged from 0.768 7 μg·mL^-1 to 2.673 8 μg·mL^-1, with the mean value of 1.622 4±0.558 2 μg·mL^-1, which could be used as the relative baseline sensitivity of A. alternata f. sp. mali to tebuconazole. Six mutants were obtained by UV irradiation and three mutants were obtained by drug adaptation. Evaluation of the resistance stability of the mutants indicated that resistance of the two moderately resistant mutants could be inherited stably, however, unstable resistance was observed for other moderately or lowly resistant mutants. Fitness penalty was observed for the mycelium growth, spore production and germination, conidial competition ability, and virulence in resistant mutants.