The International Consortium on Agricultural Biotechnology Research (ICABR)
Insect Resistant Transgenic Crops and Evaluation of related Risks
Francesca De Leo
Dipartimento di Biochimica e Biologia Molecolare
UniversitÓ di Bari
It is estimated that by the millenium the agricultural production will increase to satisfy the nutritional requirements, and the crops under cultivation need to be protected better. Yield losses vary by crop. Pimentel (1991) (1) estimates the world-wide 15.6% of the total production, valued at $ 90.5 billion (US), of the eight principal food and cash crops (coffee, potato, soybean, maize, barley, cotton, rice and wheat), was lost to animal predators, primarily insects, in 1988-90. These losses are sustained even though control measures, chiefly insecticide applications, are used on high proportion of the crop acres. The insect constitutes around half the global species diversity and a large proportion is phytophagous insect (2). The plant wild species, with a continual insects-plants co-evolution, are able to tolerate better than cultivated crops the insect attack (3). Although a large investment is being made by the agrochemical industry in the production of "safer" and more "environmental friendly" pesticides, much higher levels of protection are still required and it is clear that both conventional breeding and biotechnology have a very important contribution to make this end. It is interesting to note that there has been only a 5-fold return in research investment in chemical pesticides compared to 600-fold return in varietal resistance (4). In future, an integrated pest control programme compromising a combination of practices including the judicious use of pesticides, use of pest-free seeds, crop rotation, field sanitation, but above all, cultivating inherently resistant plant varieties and for this aim new plant biotechnology will be very useful (5).
The paper will report the different approaches used to produce insect resistant plants listed above respect to their technological maturation level: - the main approach uses d-endotoxin coding sequences derived from the bacterium Bacillus thuringensis (Bt) (6); - other strategies use plant-derived genes, such as those encoding enzyme inhibitors or lectins (7-9); - finally, new goals is to use new insecticide genes or genes expressed only in determined tissue (tissue-specific), at the most sensitive growth stages (temporal-specific) or in response to insect feeding (wound-specific) or to pyramid multiple resistance genes. For each strategies will present the specific problems related to gene individuation and isolation and related to plant transformation and regeneration.
Finally, the paper will consider a model for characterisation, valuation and management of environmental safety related to GMO release (10). In fact, experimental information can provide the basis for the analytical logic needed to construct the sequence of events arising from a hazard that lead to damage. Sources of information include: studies on the ecological impacts of potential target and nontarget effects of an organism within a laboratory model ecosystem; mathematical models; field tests; and fundamental research (e.g. physiology, metabolism, genetics) with the GMO. This analysis could contribute to increase GMO safety before the environmental release and at the same time ensure public acceptance of transgenic organism.