Contents - Faperta

11
Transgenic Resistance to Insects: Interactions with
Nontarget Organisms
Introduction
Plant resistance to insects has evolved over millions of years, and considerable progress
has been made in development and deployment of crop plants with resistance to insects.
Counter adaptation by the herbivores to the resistance mechanisms, and the response of
the natural enemies to the insect-resistant plants and the insect host determine the outcome
of such a complex interaction (Sharma and Waliyar, 2003). Such an interaction is also
infl uenced by the abiotic environmental factors. The intentional selection and breeding for
resistance to insects has led to the development of insect-resistant cultivars in several crops
and as a result the need to apply insecticides for insect control has been reduced considerably.
Insect-resistant cultivars are in general compatible with the natural enemies, although
plant resistance at times can have detrimental affects on the activity and abundance of
natural enemies. The latter has not received any adverse publicity, as the adverse effects of
insect-resistant cultivars on the nontarget organisms are still far less than those of broadspectrum
insecticides used for pest management, which may result in complete elimination
of the natural enemies of crop pests.
Signifi cant progress has been made over the past two decades in handling and introduction
of novel genes into crop plants, and has provided opportunities to increase yields,
impart resistance to biotic and abiotic stress factors, and improve nutrition. In addition to
widening the pool of useful genes, genetic engineering has also allowed the use of several
desirable genes in a single event, thus reducing the time required to introgress novel genes
into the elite background. Genes from bacteria such as Bacillus thuringiensis (Berliner) (Bt)
have been used successfully for pest control through transgenic crops on a commercial
scale (Hilder and Boulter, 1999; Sharma et al., 2000; Shelton, Zhao, and Roush, 2002). The
Bt toxins are environmentally benign (Lambert and Peferoen, 1992), and their use in
transgenic plants will avoid numerous hazards associated with the use of synthetic insecticides
in insect control. Protease inhibitors, plant lectins, ribosome inactivating proteins,