Contents - Faperta

Biotechnology, Pest Management, and the Environment: The Future 503
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Reduction in harmful effects of insecticides on nontarget organisms; and
Reduced amounts of insecticide residues in food and food products.
The benefi ts to growers of transgenic crops have been higher yield, lower input costs in
terms of pesticide use, and easier crop management (James, 2007). These factors are likely
to have substantial impact on the livelihoods of farmers in both developed and developing
countries. Transgenic corn and cotton with resistance to insects have reduced pest damage
and pesticide use, and have increased crop yield (Qaim and Zilberman, 2003; James, 2007).
However, there is considerable debate on this issue, and several claims to the contrary have
also been published in the media. In many developing countries, small-scale farmers suffer
pest-related yield losses because of technical and economic constraints. Pest-resistant
genetically modifi ed crops can contribute to increased yields and agricultural growth in
such situations. Adopting transgenic crops also offers the additional advantage of controlling
insect pests that have become resistant to commonly used insecticides. However,
deployment of insect-resistant transgenic plants should be based on an overall philosophy
of integrated pest management, and consider not only gene construct, but alternate
mortality factors, reduction of selection pressure, and development of resistance to design
effective pest management strategies. Future efforts in developing insect-resistant transgenic
plants should focus on developing:
• Transgenic plants with a wide spectrum of activity against the insect pests feeding
on a crop, but harmless to natural enemies and other nontarget organisms;
• Technologies that limit transgene expression to plant parts or growth stage of
plants that are vulnerable to insect damage;
• Transgenes that target the receptor sites in insects that have developed resistance
to conventional insecticides;
• Delivery systems for toxins from the transgenic plants to the insect hemolymph,
removing a key constraint in exploiting the transgenic approach to crop protection;
• Pyramiding of novel genes with different modes of action (Table 19.2) and with
conventional host plant resistance, and multiple resistances to insect pests and
diseases; and
• Insect-resistant plants in cereals, legumes, and oil seed crops that are a source
of sustenance for poorer sections of the society, particularly in the developing
countries.
TABLE 19.2
Candidate Genes for Use in Genetic Transformation in Crops for Resistance to
Insect Pests
Toxins Candidate Genes
Cry toxins Cry1Ab, Cry1Ac, Cry IIa, Cry9c, Cry IIB, Vip I, and Vip II
Plant metabolites Flavonoids, alkaloids, and terpenoids
Enzyme inhibitors SBTI, CpTi, and GPTi
Enzymes Chitinase and lipoxygenase
Plant lectins GNA, ACAL, WAA, and avidin
Toxins from predators Scorpion, spiders, and ants
Insect hormones Neuropeptides and peptidic hormones