In Bt cotton, Bt refers to?
Bacillus thuringiensis
A classical example of a transgenic plant is the Bt cotton. It is a new variety of cotton in which a gene isolated from a bacterium, called Bacillus thuringiensis, has been newly introduced. This gene is responsible for producing a toxin which can kill the boll worms that attack the cotton plant. Thus, the plant is free from boll worm infestation.