江西省番茄绵疫病菌对嘧菌酯的敏感性检测及抗性风险分析

为明确番茄绵疫病菌对嘧菌酯的敏感性，采用菌丝生长速率法测定了2018—2019年从江西省番茄主产区采集分离得到的58株绵疫病菌Phytophthora capsici对嘧菌酯的敏感性，并以敏感菌株YD5为亲本，通过紫外线诱导获得了4株抗性突变体，研究了突变体的生物学性状；进而采用菌丝生长速率法测定了敏感菌株YD5及其4个抗性突变体对烯酰吗啉和甲霜灵的EC₅₀值，分析嘧菌酯与烯酰吗啉和甲霜灵是否存在交互抗性。结果表明:嘧菌酯对绵疫病菌菌丝生长有较强的抑制作用，其对58个绵疫病菌的EC₅₀值介于0.1867~1.6239 μg/mL之间，平均EC₅₀值为 (0.8606±0.3318) μg/mL，58个菌株对嘧菌酯的敏感性频率分布呈正态分布，表明番茄绵疫病菌对嘧菌酯仍然较为敏感。通过紫外线诱导获得4个抗性突变体，突变体的抗药性能够稳定遗传，且在致病力与游动孢子萌发率方面与亲本菌株无显著差异，产孢量较亲本菌株显著下降。嘧菌酯与烯酰吗啉和甲霜灵之间均不存在交互抗药性。研究表明，番茄绵疫病菌对嘧菌酯具有中等抗性风险，一旦田间出现抗性菌株，应立即采取措施控制菌群的转移扩散。同时，需加强番茄绵疫病菌对嘧菌酯的田间抗性监测，在生产过程中轮用或混用不同作用机制的药剂，以避免或延缓抗药性的发展。

Sensitivity detection and resistance risk analysis of Phytophthora capsici on tomato to azoxystrobin in Jiangxi Province

In order to determine the sensitivity of Phytophthora capsici to azoxystrobin, the mycelia growth rate method was used to measure the EC₅₀ value of azoxystrobin to 58 strains of P. capsici collected from the major tomato producing areas in Jiangxi Province from 2018 to 2019. Four resistant mutants were obtained from susceptible strain (YD5) by UV irradiation, and their biological characters were investigated. The sensitivity of susceptible strain (YD5) and four resistant mutants to dimethomorph and metalaxyl was determined by mycelial growth rate method, and the cross-resistance of azoxystrobin to dimethomorph and metalaxyl was also detected. The results showed that the mycelial growth of 58 P. capsicistrains was affected by azoxystrobin, with a mean EC₅₀ value of (0.8606±0.3318) μg/mL and ranged from 0.1867 μg/mL to 1.6239 μg/mL. The sensitivity of 58 strains to azoxystrobin was fitted with a normal distribution function, which indicated that P. capsiciwas sensitive to azoxystrobin. Four resistant mutants were obtained by induction, and the resistance of them could be inherited stably. The pathogenicity and zoospore germination rates of the mutants were not significantly different from those of their parent, but the sporulation decreased significantly. There was no cross-resistance between azoxystrobin and dimethomorph, metalaxyl respectively. It was suggested that P. capsici had a moderate resistance risk to azoxystrobin. So once resistant strains appear in the field, measures should be taken immediately to control the spread of the flora. Meanwhile, the sensitivity of P. capsici to azoxystrobin should be monitored, and mixed or rotated application of fungicides with different mechanism should be considered to avoid or postpone the development of resistance.