嗜线虫致病杆菌Xenorhabdus ne matophilus HB310对3种十字花科蔬菜害虫杀虫活性的研究

嗜线虫致病杆菌XenorhabdusnematophilusHB310是与昆虫病原线虫SteinernemacarpocapsaeHB310共生的细菌。对X.nematophilusHB310杀虫活性的测定结果表明:该共生菌菌液对小菜蛾、菜粉蝶和云斑粉蝶等幼虫均有较高的胃毒杀虫活性,饲喂蘸有该菌液的甘蓝叶片72h后,小菜蛾2龄幼虫、云斑粉蝶1龄幼虫校正死亡率达100%,96h菜粉蝶1龄幼虫、云斑粉蝶4龄幼虫的校正死亡率也分别达到100%。云斑粉蝶1龄幼虫最敏感(LC50为6 4998×105cells/mL),其次为小菜蛾2龄幼虫(LC50为1 3614×106cells/mL)和菜粉蝶1龄幼虫(LC50为2 7418×106cells/mL)。深入研究发现胃毒杀虫活性物质在该菌对数生长初期就开始产生,对数生长中期已达到最大量。生测结果表明:胞内、胞外分泌物中都含有较强的胃毒杀虫活性物质,5 994×108cells/mL的原菌液、细胞及同样浓度的菌液上清和胞内上清120h对1龄菜粉蝶幼虫的胃毒杀虫活性均在90%以上,上清的胃毒活性最低,与原菌液、细胞及胞内上清的胃毒活性差异显著。X.nematophilusHB310的Ⅱ型菌菌液的胃毒杀虫活性较低,只有Ⅰ型菌的1/3左右。

Larvicidal activity of the symbiotic bacterium Xenorhabdus nematophilus HB310 against three species of cruciferae pests

Xenorhabdus nematophilus HB310 strain is an insect pathogen that is mutualistic with entomopathogenic nematode Steinernema carpocapsae HB310. X. nematophilus HB310 showed high oral insecticidal activity against Pieris rapae, Pontia daplidice and Plutclla xylostella. The bacteria killed 100% P. daplidice first-instar larvae and P. xylostella second-instar larvae within 72 h, 100% P. rapae first-instar larvae and P. daplidice four-instar larvae within 96 h. LC_50 level against P. rapae first-instar larvae,P. daplidice first-instar larvae and P. xylostella second-instar larvae was determined to be 2.741 8×10~6 cells/mL, 6.499 8×10~5 cells/mL and 1.361 4×10~6 cells/mL respectively. The bioassay results showed that the bacterium had produced oral insecticidal toxins from early log period and had very high toxicity to P. rapae first-instar larva (mortality>90%) in the middle log period. The equal volume of the bacteria broth culture, supernatant fluid, cells and intracellular supernatant all showed similar high oral toxicity. The oral toxicity of phase Ⅱ bacteria was only 1/3 of phase Ⅰ.