高毒力昆虫病原线虫共生细菌菌株的筛选及其杀虫活性的检测

昆虫病原线虫共生细菌是寄生在昆虫病原线虫肠道的一种细菌，二者互惠共生。实验采用6个不同种的菌株为筛选材料。共生细菌菌株的培养液经85%饱和度的(NH₄)_2SO4盐析，浓缩冻干得到杀虫粗提物。以粗提物注射大蜡螟Galleria mellonella、饲喂玉米螟Ostrinia furnacalis和棉铃虫Helicoverpa armigera，发现Xenorhabdus nematophilus D43、X.bovienii A54、Photorhabdus luminescens HZL和CB-8等4个菌株发酵液的粗提物对昆虫有高的血腔毒性，菌株A54对昆虫又有高的胃毒效果。由此确立A54为高毒力的菌株，其杀虫活性表现为：注射大蜡螟48 h的死亡率为80%，96 h为93.3%；粗提物饲喂玉米螟，72 h死亡率为53.3%，120 h死亡率为100%；饲喂棉铃虫，72 h死亡率为80.1%，120 h死亡率为90%。杀虫粗提物经DEAE-52柱层析分离，得到一个穿透峰和三个盐的梯度洗脱峰，其中穿透峰对昆虫有很好的胃毒效果，但没有血腔毒性；三个盐峰均有很高的血腔毒性，但没有胃毒作用。穿透峰样品饲喂2龄、3龄棉铃虫也有很好的杀虫活性，96 h 2龄棉铃虫的死亡率为65%，3龄棉铃虫的死亡率为30%；处理96 h的棉铃虫同处理前相比体重下降，未死棉铃虫体重明显低于对照。

Screening of high toxic strains from Xenorhabdus spp.and Photorhabdus spp. and assays of insecticidal activity

Xenorhabdus spp. And Photorhabdus spp.are entomopathogenic bacteria symbiotically associated with insect pathogenic nematodes of the families Steinernematidae and Heterorhabditidae. Six strains were isolated from their nematode symbiots.Crude insecticidal material was precipitated with ammonium sulfate at 85% saturation from cell-free culture.By the means of bioassay, Xenorhabdus bovienii strain A54 was found highly toxic to insects. Injection of the toxin killed 93.3% of Galleria mellonella larvae within 96 h. Feeding artificial diet with the toxin, the mortalities of larvae of Ostrinia furnacalis and Helicoverpa armigera were 100% and 90% within 120 h respectively. Isolated by DEAE-52 column,a penetrating peak and three NaCl eluting peaks were obtained from the crude extract.Materials from the penetrating peak had oral insecticidal activity against H.armigera,but no toxicity when injected into the hemolymph of G.mellonella. Materials from three NaCl eluting peaks had high toxicity when injected, but no toxicity when given orally. Meanwhile, feeding artificial diet with the toxin, the mortalities of 2-instar and 3-instar larvae of H.armigera were 65% and 30% within 96 h respectively.