Transformation-induced mutations in transgenic plants: analysis and biosafety implications.

Plant transformation has become an essential tool for plant molecular biologists and, almost simultaneously, transgenic plants have become a major focus of many plant breeding programs. The first transgenic cultivar arrived on the market approximately 15 years ago, and some countries have since commercially approved or deregulated (e.g. the United States) various commodity crops with the result that certain transgenic crop plants, such as herbicide resistant canola and soya and pest resistant maize, are currently grown on millions of acres. Advocates for the use of genetic engineering as a plant breeding tool claim its precision provides a major advantage over other plant breeding techniques. The presumption is that genetic engineering results in (1) only specific and known genotypic changes to the engineered plant (the simple insertion of a defined DNA sequence the transgene) and (2) only known and specific phenotypic changes [the intended trait(s) encoded by the transgene]. This presumption has strongly influenced biosafety regulation. Regulators typically assume that the plant transformation methods used to introduce a transgene into the plant genome are mostly irrelevant to the risk assessment process and that the major source of risk in transgenic crop plants arises from the transgene itself. The focus of this review is a scientific assessment of the precision of current crop plant transformation techniques.