Abstract: Insecticidal engineered bacteria of cotton are recombinant bacteria by introducing the cryIA© gene from Bacillus thuringiensis subsp. Kurstaki into the chromosome of Bacillus cereus(Bc9102) which is a dominant endophytic bacterium in cotton. In vitro bioassays with cotton bollworm (Helicoverpa armigera) was conducted and the results showed: at each concentration level, engineered strains HE-1,HE-2,ME14-2,ME14-3 and MK14-1 had a higher insecticidal activity than Bt strain HD-73, causing 96.7%,83.3%,93.3%,83.3%,80.0% mortality respectively at the highest concentration while Bt HD-73 had 80% mortality. The concentration mortalitey curves of these strains showed a linear correlation. In planta bioassays, the results showed that insecticidal activity of cotton injected or sprayed with engineered bacteria was obviously better than that of cotton seedtreated with engineered bacteria. For example, engineered strain HE-1 had larval mortality respectively 90.0%、76.0% and 23.3% after injection,spraying and seedtreatment 4 weeks. At the same time, engineered bacteria restrained the development of cotton bollworms.

Key words: Bacillus cereus, insecticidal engineered bacteria, cotton bollworms