Sceening Of New Bacilluds Thuringiensis Strains With High Insecticidal Activity And Cloning Of Cry2Ab Gene

25 isolates of Bt were obtained from 500 soil samples from Hebei province in China. The bioassay in lab showed WZ-2,WZ-7,WZ-4,WZ-5 were high toxicity against five lepidoptera pestsjncluding Helicoverpa armigera, Spodoptera exigua, Pieris rapae, Plutellaxylostella, Ostriniafurnacalis.Especially, LC50 of WZ-7 to 3 pests(Helicoverpa armigera, Ostriniafurnacalis, Spodoptera exigud) respectively was 3.30+105cells/mL. 5.21+106cells/mL and 1.16+105cells/mL. WZ-9 strain exhibited potent larviciddal toxicity to Henosepilachna vigintioctomaculata larvae ( LC50=2.95+107cells/m L).WZ-7 strain cry-type genes were identified by PCR-RFLP method.The results showed it contain cry1Ab, ,crylCa, cry1Ba, cry2Ab, cry1Ial,and all genes of WZ-7 were located on plasmids.A pair of specific primer was designed for amplification of cry2Ab gene.The amplified products of cry2Ab gene was directly inserted into pUCm-T vector and transformed into E. coli strain DH5 a.The linkage sequences of cry2Ab gene from Bt strain WZ-7 were cloned and sequenced,and it encoded a crystal protein that was composed of 633 amino acids with M.W. 70.6kDa and isoelectric point pI8.96, This gene was registered in GenBank ,The accession number was AY297091.