Some strains of Bacillus thuringiensis produce proteins that kill certain insects such as lepidopterans (tabacco budworm, armyworm), coleopterans (beetles) and dipterans (files, mosquitoes). Bacillus thuringiensis forms protein. Crystals which contain a toxic insecticidal protein. The gene responsible for the production of this toxic protein is introduced genetically into the cotton seeds protects the plants from Bollworm, a Major pest of cotton. The worm feeding, on the leaves of Bt. Cotton plant becomes lethargic and sleepy thereby causing less damage to the plant. Use of Bt. Cotton has led to 3-27% increase in cotton yield in countries where it is grown.
The toxin is coded by a gene named 'cry'. The proteins encoded by the genes cry IAc and cry IIAb control the cotton boll worms and cry IAb controls corn borer.
