Bacillus thuringiensis or Bt is a naturally occurring soil bacterium mostly used by farmers to control Lepidopteran insects because of its toxin producing ability. Scientists have introduced the gene responsible for making the toxin into a range of crops, including cotton. Bt expresses the qualities of the insecticidal gene throughout the growing cycle of the plant. Cotton and other monocultured crops require an intensive use of pesticides as various types of pests attack these crops causing extensive damage. Over the past 40 years, many pests have developed resistance to pesticides.
Cotton crops are very susceptible to pest attacks and use up more than 10 per cent of the world's pesticides and over 25 per cent of insecticides. As of now, cotton is the most popular of the Bt crops. The Bt gene was isolated and transferred from a bacterium bacillus thurigiensis to American cotton. The American cotton was subsequently crossed with Indian cotton to introduce the gene into native varieties. So far, the only successful approach to engineering crops for insect tolerance has been the addition of Bt toxin, a family of toxins originally derived from soil bacteria. The Bt toxin contained by the Bt crops is no different from other chemical pesticides, but causes much less damage to the environment.
Bt cotton is in many ways an ideal candidate for introduction as a transgenic commercial crop. It is basically grown as a fibre crop, while cotton seed oil used for consumption is free of proteins, including Bt protein. Environmental safety concerns are negligible because of the limited movement of heavy cotton pollen and the existence of natural genetic barriers that preclude out crossing with native Indian cotton. There is also no known compatibility of cultivated cotton with any wild relatives occurring in India. Cotton is not found as a weed in the global production systems and Bt is unlikely to confer any advantage that would result in Bt cotton establishing as a weed.
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