Isolation, biochemical and crytype gene characterization of Bacillus thuringiensis　strains with high toxic to Plutella xylostella

Key Words： Bacillus thurigiensis, identification, insecticidal activity, cry/cyt genes

Abstract：    The insecticidal activities of ten strains of Bacillus thuringiensis isolated from diseased Plutella xylostella (L.) larvae were characterized. All strains caused >80% larval mortality and the strain DBW902 had the highest insecticidal activity with an LC50 of 13.99 mg/L at 48 h. The biochemical characteristics and cry/cyt genes of each strain were determined. High insecticidal activity coincided with the detection of at least one cry1A or cry2A family gene. The biochemical characteristics of the strains, DBW904, DBW93 and DBW962 were homologous to B. thuringiensis subsp. and Shandongiensis, but not the other strains. The identification of these 10 B. thuringiensis isolates with moderate to high insecticidal activity against P. xylostella is promising for the control of this pest in northeastern China.