ABSTRACT
There is a need for planned introduction of genetically modifi ed organisms into the environment. There are concerns that the deployment of transgenic plants will lead to development of resistance in insects and gene fl ow between closely related species and the unrelated species in the ecosystem. While some of these concerns may be real, others seem to be highly exaggerated. Therefore, careful thought should be given to the production and release of transgenic crops in different agroecosystems. A number of ecological issues, including gene fl ow, need to be addressed while considering the production and deployment of transgenic crops for insect control. The greatest risk of a transgenic plant released into the environment is its potential spread to other areas to become a weed. Genes from unrelated sources may change the fi tness and population dynamics of the hybrids between native plants and the wild species. However, there are no records of a plant becoming a weed as a result of plant breeding (Cook, 2000). This is mainly because of:
Low risk of crop plants to the environment;• Extensive testing of the crop varieties before release; and• Adequate management practices to mitigate risks inherent in crop plants.•
Plant breeding efforts have tended to decrease rather than increase the toxic substances, as a result making the improved varieties more susceptible to insect pests. However, there is a feeling that genes introduced from outside the range of sexual compatibility might present new risks to the environment and human beings. However, many such apprehensions are not supported by data. A study conducted by the National Academy of Sciences (NAS, 1987) has concluded that:
There is no evidence of hazards associated with DNA techniques.• The risks, if any, are similar to those with conventional breeding techniques.• The risks involved are related to the nature of the organism rather than the process.•
There is a need for risk assessment of the likely spread of transgenes via pollen through insect pollinators, largely bees (honeybees and bumblebees) to other crops, or to sexually compatible wild relatives. Insect-mediated pollen and gene fl ow is a function of the deposition of viable and compatible pollen from donor to recipient plants along insect foraging routes, and of the spatial dynamics of those foraging routes within the foraging areas. Knowledge of bee foraging behavior will be useful to design appropriate confi nement strategies for experimental releases, monitoring protocols, and mitigation procedures for risk management. Crucial data are lacking for the development of a credible scientifi c basis to confi rm or deny environmental risks associated with ecological roles of lepidopterans exploiting specifi c wild relatives of Bt transgenic crops and escape of Bt transgene constructs to wild relatives (Letourneau, Robinson, and Hagen, 2003).
