tions are made for commercial release. An unexpected or unintended effect does not imply a health hazard, although clearly a plant expressing novel and unexpected characteristics warrants closer inspection prior to commercial release.
A large body of transgenic plant material is developed by university and government laboratories investigating aspects of rDNA that are not related to commercial interests. The Organization for Economic Cooperation and Development (OECD) lists more than 10,000 field trials with GE plants that were conducted between 1986 and 1999. Most of these authorized trials were conducted on plants genetically engineered by public universities and government research institutions, not for commercial release but to test the plants for unexpected or unintended results (see OECD, 2000). Consequently, most of the information on unexpected or unintended results comes from these sources.
Because GE crops are regulated to a greater degree than are conventionally bred, non-GE crops, it is more likely that traits with potentially hazardous characteristics will not pass early developmental phases. For the same reason, it is also more likely that unintentional, potentially hazardous changes will be noticed before commercialization either by the breeding institution or by governmental regulatory agencies.
The following are among the examples of unexpected or unintended characteristics that are often cited in the scientific literature.
Bt (Bacillus thuringiensis) corn was developed to help farmers protect corn crops from insect pests, particularly the European corn borer and, more recently, the corn root worm. An unexpected effect in this product was a substantial reduction in mycotoxins, which can adversely affect animal and human health. Researchers hypothesized that this is because mycotoxin production is stimulated by fungal spores that infect corn when worms bore into and injure the plant. In the absence of insect damage (as in the Bt corn plants), there is reduced opportunity for pathogenic fungal spores to infect the plant and therefore less opportunity to generate the associated and undesirable mycotoxins (Munkvold et al., 1997, 1999).
Saxena and Stotzky (2001) reported that three Bt corn varieties increased their stem lignin content relative to their respective non-Bt isogenic parents. Since the increase was found in more than a single variety, this suggests that the lignin increase is directly associated with the inserted DNA and is not simply an isolated coincidence. However, increased lignin content has not been recorded in other Bt corn lines, so it is uncertain whether the reported increase was due to the rDNA insertion, the presence of Bt endotoxin, or some other mechanism. Al-