A biotechnology solution to insect pests in the case of cotton
The bacterium Bacillus thuringiensis, or Bt, is a naturally occurring soil bacterium, and produces proteins that kill insects. Sprays containing Bt bacteria have been used as pesticides on farms, including organic farms, for many years.
By the early 1990s the cotton bollworm had developed resistance to most chemical pesticides. Scientists working for the US company Monsanto developed a cotton variety called Ingard®, which contains a gene derived from the Bt bacterium.
When the gene is inserted into cotton plants a toxic protein is produced that kills the bollworm caterpillars. These proteins are known as Bt toxins. The poison stays in the leaves and does no harm until the bollworm eats the leaf tissue. It is very specific – it only kills the bollworm caterpillars and very closely related species. It does not affect humans and other animals.
In the 1990s, CSIRO Plant Industry scientists used licensed Monsanto genes to develop cotton varieties containing a Bt gene that were suitable for Australian conditions. This variety was called Ingard® cotton.
In 1999 about 40 million hectares of Bt GM cotton were planted worldwide. In that same year, about one third of Australia’s cotton crop (about 100,000 hectares) was Bt cotton.
Some bollworm caterpillars may be resistant to Bt, which means that Bt cotton crops still need to be sprayed with insecticides to kill any surviving caterpillars. However, the amount of insecticide spray used on cotton crops was greatly reduced due to the introduction of Ingard® cotton.
The CSIRO has since created a new form of Bt cotton known as Bollgard®II, also using licensed Monsanto genes. This new cotton is Ingard® cotton plus a second, different, insecticidal gene from Bacillus thuringiensis. The addition of this second gene significantly reduces the possibility of the bollworm developing resistance to the Bt toxins.
In 2004, 80% of the Australian cotton crop was Bollgard®II.
For more information about Bt cotton, go to: http://www.csiro.au/pubgenesite/research/ cotton/cotton_with_build_short.htm
And on GM cotton in Australia: www.afaa.com.au/resource_guides/Resource_Cotton.pdf
Several companies, such as Monsanto, Syngenta, Dow AgroSciences, and Bayer CropScience have developed varieties of cotton with built-in resistance to the bollworm, and other scientists are researching the use of viruses and venoms in order to kill cotton pests.