Screening of Bacillus thuringiensis strain with broadspectrum and high toxicity and cloning of its insecticidal crystal protein gene

After the determination of insecticidal activity,one Bacillus thuringiensis strain,showing high toxic to Pieris rapae,Plutclla xylostella and Chilo suppressalis,was obtained and named Bt X-2.Degenerate primers were designed based on the N-terminal partial sequence of Cry1 to amplify the corresponding DNA sequence by touchdown PCR.The amplified fragment,with the length of 3 468 bp,encoding(1 155) amino acid with M_r=130 780 and pI=5.06.The amino acid sequence of Cry1Ab X-2 gene showed more than 95% identity to other Cry1Ab,and it was registered in GenBank(Accession No.AY847289).