Studies on insecticidal activity of metabolites of symbiotic bacteria associated with entomopathogenic nematodes | 2株昆虫病原线虫共生菌发酵物杀虫活性研究

Chinese. 研究嗜线虫致病杆菌X. nematophila YL001（YL001菌株）和伯氏致病杆菌X. bovienii _YL002（YL002菌株）发酵物的杀虫活性, 为昆虫病原线虫共生菌生物农药的开发和抗虫基因工程研究提供理论依据。采用注射法、浸液法及小叶碟添加法，分别测定了YL001和YL002菌株发酵无菌滤液，对大蜡螟、粘虫、小菜蛾及棉铃虫的血腔毒性及毒杀、生长抑制和拒食活性，并对其特性进行了初步检测。YL001和YL002菌株无菌滤液对大蜡螟和粘虫5龄幼虫均具有较高的血腔毒性，用其不同培养时间的无菌滤液处理大蜡螟和粘虫，48 h后大蜡螟的死亡率均为100%，粘虫的死亡率随共生菌培养时间的延长而逐渐降低。YL001和YL002菌株的无菌滤液对小菜蛾3龄幼虫和棉铃虫初孵幼虫的毒杀活性和生长抑制活性均较低，对5龄棉铃虫幼虫的拒食活性也很低，48 h的平均拒食率分别为24.0%和29.0%。2菌株无菌滤液经50 ℃处理后，对大蜡螟5龄幼虫的血腔毒性无影响；经70 ℃处理后毒力明显降低。2菌株无菌滤液对蛋白酶较敏感。YL001和YL002菌株对害虫有较高的血腔毒性，但毒杀、生长抑制及拒食活性较低，其血腔毒素可能主要是蛋白类物质。

English. The study evaluated the insecticidal activity of metabolites of Xenorhabdus nematophila YL001 and Xenorhabdus bovienii YL002 which were isolated from its nematode symbiont, Steinernema sp.YL001 and Steinernema sp.YL002 obtained from the soil from Yangling, China to provide the theoretical basis for the development of insecticide and the genetic engineering. The injectable toxicity of the cell-free aqueous filtrates of fermented liquid of YL001 and YL002 strains for the 5th larvae of Galleria mellonella and the 5th larvae of Mythimna separate were tested with injecting method. The stomach toxicity and growth inhibition activity against the 3rd larvae of Plutella xylostella and the neonate larvae of Helicoverpa armigera were assayed with leaf dipping method. The antifeeding activities against the 5th larvae of Helicoverpa armigera were assayed with leaf-disk method. The results showed that both symbiotic bacteria had highly injectable toxicity for Galleria mellonella, with the mortality of 100% after 48 h when injected the cell-free aqueous filtrates of fermented liquid of different culture time, but the mortality of Mythimna separate decreased with prolonged culture time. The stomach toxicity and growth inhibition activity of the cell-free aqueous filtrates of YL001 and YL002 strains against the 3rd larvae of Plutella xylostella and the neonate larvae of Helicoverpa armigera were lower. The 48 h antifeeding activities of YL001 and YL002 strains against the 5th larvae of Helicoverpa armigera were 24.0% and 29.0% respectively. The injectable toxins were possible proteins. The metabolites of Xenorhabdus nematophila YL001 and Xenorhabdus bovienii YL002 have higher injectable toxicity for pests, but the stomach toxicity, growth inhibition activities and antifeeding activities are lower.