Genetic engineering of crops as potential source of genetic hazard in the human diet

The benefits of genetic engineering of crop plants to improve the reliabili ty and quality of the world food supply have been contrasted with public co ncerns raised about the food safety of the resulting products. Debates have concentrated on the possible unforeseen risks associated with the accumula tion of new metabolites in crop plants that may contribute to toxins, aller gens and genetic hazards in the human diet. This review examines the variou s molecular and biochemical mechanisms by which new hazards may appear in f oods as a direct consequence of genetic engineering in crop plants. Such ha zards may arise from the expression products of the inserted genes, seconda ry or pleiotropic effects of transgene expression, and random insertional m utagenic effects resulting from transgene integration into plant genomes. H owever, when traditional plant breeding is evaluated in the same context, t hese mechanisms are no different from those that have been widely accepted from the past use of new cultivars in agriculture. The risks associated wit h the introduction of new genes via genetic engineering must be considered alongside the common breeding practice of introgressing large fragments of chromatin from related wild species into crop cultivars. The large proporti on of such introgressed DNA involves genes of unknown function Linked to th e trait of interest such as pest or disease resistance. In this context, th e potential risks of introducing new food hazards from the applications of genetic engineering are no different from the risks that might be anticipat ed from genetic manipulation of crops via traditional breeding. In many res pects, the precise manner in which genetic engineering can control the natu re and expression of the transferred DNA offers greater confidence for prod ucing the desired outcome compared with traditional breeding. (C) 1999 Else vier Science B.V. All rights reserved.