抗甲霜灵辣椒疫霉菌的环境适合度

Environmental fitness of metalaxyl-resistant isolate of Phytophthora capsici

摘要:

摘要:【目的】研究抗甲霜灵辣椒疫霉菌的环境适合度，对于评估甲霜灵防治辣椒疫霉的抗药性风险具有重要意义。【方法】以室内药剂驯化的抗甲霜灵辣椒疫霉菌株Pc2-3为研究对象，分析比较其与原始敏感菌株Pc2的主要生物学特性、生长竞争力、致病力及土壤适合度等环境适合度指标。【结果】Pc2-3孢子囊产生量(3 d后)、孢子囊释放率(24 h后)和游动孢子萌发率(8 h后)分别是Pc2的0.44、0.09和0.54倍。Pc2-3可生长温度和pH范围及最适生长温度与Pc2基本一致，但菌丝生长速率低于Pc2。竞争力测定显示，在胡萝卜(CA)平板培养条件下，Pc2-3生长极显著弱于Pc2。盆栽致病试验显示，Pc2-3对辣椒植株的致病率为14.3%，明显低于Pc2(88.6%)。两者等量混合后接种，辣椒植株的发病率为75.7%，接近单独接种Pc2时的发病率，且所有病株分离出的辣椒疫霉菌均为甲霜灵敏感型。分别将Pc2-3和Pc2游动孢子加入自然土壤培养20 d后，实时定量PCR检测显示Pc2-3数量是Pc2的0.28倍，当土壤中含有300 mg/kg干土的甲霜灵，则前者为后者的0.42倍。此外，2个菌株最适存活土壤温度和湿度基本一致，当土壤温度和湿度利于辣椒疫霉存活时，Pc2-3土壤适合度显著低于Pc2，不利于辣椒疫霉存活时，Pc2-3土壤适合度略低于Pc2。【结论】抗甲霜灵菌株Pc2-3环境适合度弱于原始敏感菌株Pc2。

关键词:关键词:辣椒疫霉，甲霜灵抗药性，环境适合度

Abstract:

Abstract:［Objective］ The environmental fitness of metalaxyl-resistant isolate of Phytophthora capsici was studied for assessing the risk of metalaxyl-resistant P．capsici．［Methods］We studied the main biological characteristics，competitive ability on plate，pathogenicity on pepper plant and adaptability in soil of the laboratory-induced metalaxyl-resistant isolate of P．capsici (Pc2-3 strain)，with the metalaxyl-sensitive isolate (Pc2 strain，the wild-type) as the control.［Results］The zoosporangia production，releasing rate of zoosporangia and germination rate of zoospores of Pc2-3 were less than that of Pc2．The temperature range，optimum temperature range and initial pH range for mycelia growth of Pc2-3 were consistent with that of Pc2，but mycelia growth rate of Pc2-3 was lower than that of Pc2． Pc2-3 exhibited significantly weak competitive ability compared with Pc2 on carrots plate．Disease incidence of pepper inoculated with Pc2-3 (14.3%) was significantly lower than that of Pc2 (88.6%)．When pepper plant was inoculated by mixtures of zoospore suspension of Pc2-3 and Pc2 at same ratio，the disease incidence，closing to that by Pc2 strain，was 75.7%．And all the strains isolated from diseased plants in the treatment were metalaxyl-sensitive．The density of P．capsis Pc2-3 was 0.28 times of Pc2 after the soil inoculated with Pc2-3 and Pc2 respectively at same zoospores density was incubated for 20 days．Otherwise，the ratio of Pc2-3 to Pc2 was 0. 42 if the metalaxyl concentration in the soil was 300 mg/kg dry soil．No matter the soil temperature and humidity were beneficial to survival of P．capsici or not，Pc2-3 showed lower soil adaptability than Pc2．［Conclusion］ The environmental fitness of metalaxyl-resistant P．capsis Pc2-3 was weaker than the metalaxylsensitive strain Pc2 (the wild-type)．

Key words:Keywords: Phytophthora capsici，metalaxyl-resistance，environmental fitness