Abstract: Bacillus thuringiensis(Bt) is most widely studied and used as insecticidal microbe for its high insecticidal activity and safety. In order to search new Bt source，71 soil samples were collected from different orchards of Hebei province in China including pear orchards，g rape orchards，jujube orchards and chestnut orchards. 41 Bt isolates were obtained from 71 soil samples using sodium acetate via antibiotics method. These Bt isolates were characterized based on their insecticidal activity，crystal protein shape，sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) ，and PCR analysis using novel general and specific primers for cry genes. Six types of cry gene，cry1， cry7，cry8，cry19，cry26-28 and cry32，were found in 39 Bt isolates，There ware still two Bt strains which cry gene of did not be identified. Most isolates showed a major protein band of 130 kDa in SDS PAGE gel. The spore-crystal mixtures of XPZ-6，XPZ-8，XPZ-9，XPZ-39 and XPZ-42 strains all showed high toxicity against the larvae of Plutella xylostella， Helicoverpa armigera，Ostrinia furnacalis and Hyphantria cunea，moreover，the insecticidal activities of XPZ-39 strain were highest (＞ 97% mortalities) . XPZ-28 and XPZ-46，cry genes of which did not identified，showed insecticidal activities to larvae of Plagiodera versicolora and Gastrophysa atrocyanea respectively.

Key words: Bacillus thuringiensis, cry gene, Insecticidal crystal proteins, Insecticidal activity

CLC Number: 

• S43