Results of insect infestation on Bt (right) and non-Bt (left) cotton bolls.
Bt cotton hybrids exhibits excellent control of American Boll worm and reduces the use of insecticides leading to create eco-friendly environment without compromising on profitable yield.
As studied earlier, Bt stands for Bacillus thuringiensis - a soil bacterium which contains a toxic gene called Bt gene. Strains of the bacterium Bacillus thuringiensis produce over 200 different Bt toxins, each harmful to different insects. Most notably, Bt toxins are insecticidal to the larvae of moths and butterflies, beetles, cotton bollworms and some flies, but are harmless to other forms of life. The gene coding for Bt toxin has been inserted into cotton as a transgene (A transgene is a gene or genetic material that has been transferred naturally, or by any of a number of genetic engineering techniques from one organism to another.
The introduction of a transgene (called "transgenesis") has the potential to change the phenotype of an organism), causing it to produce this natural insecticide in its tissues. In many regions, the main pests in commercial cotton are lepidopteran larvae, which are killed by the Bt protein in the genetically modified cotton they eat. This eliminates the need to use large amounts of broad-spectrum insecticides to kill lepidopteran pests. This spares natural insect predators in the farm ecology and further contributes to non-insecticide pest management. Specific Bt toxin genes were isolated from Bacillus thuringiensis and incorporated into the several crop plants such as cotton. The choice of genes depend upon the crop and the targeted pest, as most Bt toxins are insect-group specific. The toxin is coded by a gene named cry. There are a number of them, for example, the proteins encoded by the genes cryIAc and cryIIAb control the cotton bollworms, that of cryIAb controls corn borer.
Hence through genetic engineering, the gene is inserted into the cotton seed. Due to this the toxin will no more be harmful to the plant because bt gene now becomes a part of it just like other genes. Put simply, it gets adapted. Along with this, a gene responsible for high yield is chosen from another cotton variety and fused into the same seed. Finally you have a seed which is pest resistant and high yielding. Needless to say this seed grows into HYPR(High Yielding Pest Resistant) cotton crop which we popularly call Bt Cotton.