辣椒疫霉(Phytophthora capsici Leonian)不同发育阶段对嘧菌酯的敏感性研究

 细胞色素bc₁位点抑制剂包含作用于线粒体内膜外壁CoQ氧化位点抑制剂(Q_oIs)和作用于线粒体内膜内壁CoQ的还原位点抑制剂(Q_iIs)。从未使用过Q_oIs和Q_iIs的江苏省南京市和安徽省和县随机采集分离获得48个辣椒疫霉单游动孢子囊菌株,并测定了它们不同发育阶段对嘧菌酯的敏感性。结果表明,辣椒疫霉菌丝生长对嘧菌酯的敏感性最低,EC₅₀值范围在1.225~86.100 μg/mL,平均值为(21.041±14.397)μg/mL,其活性低于甲霜灵47.7倍;游动孢子囊形成和萌发对嘧菌酯的敏感性较高,EC₅₀值范围分别在0.006~0.996 μg/mL和0.053~0.334 μg/mL,平均值分别为(0.161±0.126)μg/mL和(0.155±0.023)μg/mL,其活性高于甲霜灵516.8倍;游动孢子萌发对嘧菌酯的敏感性最高,EC₅₀值范围在(0.018~0.111)μg/mL,平均值为(0.057±0.011)μg/mL,活性是甲霜灵的142.4倍。离体生物测定结果表明,水杨肟酸对嘧菌酯抑制菌丝生长的增效作用最强,对游动孢子囊形成的增效作用次之,而对游动孢子囊和游动孢子萌发过程的增效作用则不明显。

Baseline sensitivity of different morpha of Phytophthora capsici Leonian to azoxystrobin

Cytochrome bc₁ inhibitors include Quinone outside Inhibitors(Q_oIs), such as azoxystrobin, (which bind) to quinone oxidizing pocket of the cytochrome bc₁ enzyme complex(complex Ⅲ), and Quinone inner Inhibitors(Q_iIs) binding to quinone deoxidizing pocket of complex Ⅲ. 48 singlesporangia isolates of Phytophthora capsici, causing capsicum epidemic disease, were collected and purified from Nanjing, Jiangsu province and Hexian, Anhui province where Q_oIs and Q_iIs had not been used previously. Sensitivities of different morpha of P. capsici life cycle to azoxystrobin were determined. Mycelial growth of P. capsici was the least affected by azoxystrobin, with mean EC₅₀ value(21.041±14.397) μg/mL ranging from 1.225 to 86.100 μg/mL. Value of azoxystrobin EC₅₀ was lower than that of metalaxyl 47.7 times. The mean EC₅₀ values of azoxystrobin inhibiting sporangia formation and germination of P. capsici were(0.161±0.126) μg/mL and(0.155±0.023) μg/mL ranging from 0.006 to 0.996 μg/mL and 0.053 to 0.334 μg/mL, respectively. Its activity was 516.8 folds as that of metalaxyl. Germination of encysted zoospores of P. capsici was most sensitive to azoxystrobin, and EC₅₀ distributed from 0.018 to 0.111 μg/mL with mean value(0.057±0.011) μg/mL. This value was 142.4 times lower than that of metalaxyl. Salicylhydroxamic acid had significant synergetic action to azoxystrobin in inhibiting P. capsici mycelial growth and sporangia formation in vitro, however, it had no synergetic action in inhibiting sporangia and zoospore germination.