Several important crop plants are attacked by a variety of insects and pests. Bacillus thermogenesis bacterium is known as Bt in short. It was discovered that this was instrumental in causing the death of larvae of four species of Bollworm. This bacterium was registered as a biopesticide in the U.S.A. in 1961. A gene called a cry gene is found in this bacterium. This gene (cry gene) codes for a protein which kills the insect pests. This gene was separated from Bt bacterium and was incorporated in the genome of the cotton plant. The cotton variety so developed is called Bt cotton or killer cotton. This cotton is resistant to the Bollworm.
