Insect resistant transgenic plants

Serious losses in crop yields are caused due to insect pests. There are about 67,000 pest species that damage crops. Of these, 9,000 species are insects and mites, which are responsible for major yield losses in several of our important crops, particularly the tropical crops. Therefore, transfer of genes(s) providing resistance against insects in crop plants leading to the production of insect resistant transgenic crops has been major application of biotechnology in agriculture sector.

The insect resistant transgenic crops carrying Bt toxin genes have been shown to be very effective in controlling insect damage and are actually better than the currently used methods of insect control through insecticidal sprays (consult Chapter 47 for biopesticides).

A new insect resistance technology involving the use of smart proteins (computer designed) and VIPs (discovered in 1997) will certainly be utilized in future. Pyramiding of different genes active against the same insect will also become common in future. It is predicted that as many as five or more foreign genes against the same insect will be available in most insect resistant transgenic crops by th year 2005.

Some of the novel systems include the following : (i) Control of insect growth through toxicity of their purine metabolic pathway, (ii) use of Beauveria virulent with an active avaricide against Lepidoptera; (iii) Use of 3-hydroxy-steroid oxidase against Lepidoptera and boll weevil; (iv) use of a gene for carbonarin anti insectant metabolites isolated from Aspergillus carbonarius.

However, the use of smart proteins, VIPs, engineered proteins (computer aided) and manipulation of metabolic pathways (e.g. production of azadirachtin, a toxic compound from neem tree) are believed to provide long term insect resistant transgenic plants.