一株对苹果树鳞翅目害虫高毒力的苏云金芽胞杆菌YX-1

苏云金芽胞杆菌Bacillus thuringiensis(Bt)YX-1是从土壤中分离的对多种鳞翅目害虫具有杀虫活性的新菌株。为了探索该菌株在果树上应用的可行性,本研究测定了Bt YX-1菌株对苹果树上6种鳞翅目害虫的杀虫毒力,同时对该菌株的晶体形态特征、蛋白型、生长特性、基因型等进行了分析。结果表明,Bt YX-1菌株产生菱形伴胞晶体,SDS-PAGE分析表明该菌株表达的主要蛋白条带分子量约为130ku和60ku;基因型鉴定表明,Bt YX-1菌株含有cry1Ac、cry2Ac、cry1I、vip3Aa和cry34-35基因;生物活性测定表明,Bt YX-1菌株的孢晶混合物对美国白蛾Hlyphantria cunea、棉铃虫Helicoverpa armigera、斜纹夜蛾Prodenia litura、梨小食心虫Grapholitha molesta、苹小卷叶蛾Adoxophyes orana以及苹掌舟蛾Phalera flavescens的LC50分别为14.48、2.72×103、6.24×104、1.01×102、3.52×104、4.73×103mg/L,均低于标准菌株Bt HD-1的LC50。发酵上清液的杀虫活性很低,2龄棉铃虫幼虫的死亡率仅为8.33%,但是该上清液能显著提高孢晶混合物的毒力,说明上清液中含有增效物质。研究结果表明该菌株具有进一步开发为商品制剂的潜力。

Characteristics of Bacillus thuringiensis strain YX-1 with high toxicity to Lepidopteran apple pests

A strain of Bacillus thuringiensis （Bt） strain,YX-1,with high toxicity to apple tree pests was isolated from soil in Hebei.In order to explore the feasibility of using this to control apple pests the toxicity of Bt YX-1 to some apple tree pests was assayed.The crystal shape,protein type,genotype and growth characteristics of Bt YX-1 were also observed and analyzed.A light microscope indicated that Bt XY-1 has crystals with a bipyramidal shape.SDS-PAGE analysis indicates that this strain produced 130 ku and 60 ku protein bands.PCR-RFLP analysis revealed the presence of cry1Ac,cry2Ac,cry1I,vip3Aa and cry34-35 genes.The bioassay results show that Bt YX-1 was highly toxic to larvae of Hlyphantria cunea,Helicoverpa armigera,Prodenia litura,Grapholitha molesta,Adoxophyes orana and Phalera flavescens with respective LC50 of 14.48 mg/L,2.72×103 mg/L,6.24×104 mg/L,1.01×102mg/L,3.52×104 mg/L and 4.73×103 mg/L.The toxicity of Bt YX-1 was higher than that of Bt HD-1.Although supernatant from a culture broth of Bt YX-1 showed very low insecticidal activity （8.33% mortality） against 2nd instar larvae of H.armigera it markedly improved the toxicity of a mixture of spores and crystals.Our results show that the Bt YX-1 may prove valuable as a microbial control agent for lepidopteran pests or apple crops.