Natural variation in crop composition and the impact of transgenesis

To the Editor:

Compositional equivalence of crops improved through biotech-derived transgenic, or genetically modified (GM), traits and their conventional (non-GM) comparators is an important criterion in breeding as well as a key aspect of risk assessments of commercial candidates. We present here an analysis evaluated from compositional data on GM corn and GM soybean varieties grown across a range of geographies and growing seasons with the aim of not only assessing the relative impact of transgene insertion on compositional variation in comparison with the effect of environmental factors but also reviewing the implications of these results on the safety assessment process. Specifically, our analysis includes evaluation of seven GM crop varieties from a total of nine countries and eleven growing seasons. On the basis of our data, we conclude that compositional differences between GM varieties and their conventional comparators were encompassed within the natural variability of the conventional crop and that the composition of GM and conventional crops cannot be disaggregated.

Plant breeding programs expect to either maintain compositional quality during enhancement of other agronomic traits or improve crop compositional quality through intended changes in the levels of key nutrients or antinutrients. Over the past two decades, one of the most successful approaches to enhancing agronomic traits in crops is the insertion of trait-encoding genes using the techniques of modern biotech. Compositional equivalence between GM crops and conventional (non-GM) comparators is an important breeding goal but is also often considered to provide an "equal or increased assurance of the safety of foods derived from genetically modified plants" (1). Comparative compositional studies are therefore included as a significant component of risk assessments of new GM crops. As a consequence, a large body of high-quality compositional data generated according to principles outlined in the Organization for Economic Cooperation and Development (OECD; Paris) consensus documents (2) are available. On a product-by-product basis, compositional equivalence of GM crops and their conventional comparators has been demonstrated in potato, cotton, soybean, corn, rice, wheat and alfalfa (for a list of references describing compositional and omics comparisons of GM and non-GM comparators, see Supplementary References). In addition to the compositional studies conducted within regulatory programs, biochemical studies on GM crops have been extensively pursued by public and private research sectors. Although there are complexities in the interpretation of modern profiling technologies, and no standardized framework for comparisons, the lack of variation between GM crops and their conventional comparators at the transcriptomic, proteomic and metabolomic level has been independently corroborated. These profiling evaluations extend to a wide range of plants including wheat, potato, soybean, rice, tomato, tobacco, Arabidopsis and Gerbera (see Supplementary References).

These, and other studies (e.g., refs. 3-5), have also suggested a high degree of natural variability inherent to crop biochemical and metabolite composition. It is therefore reasonable to ask if changes in composition associated with modern transgenic breeding practices are different in scope from those attributable to natural genotypic and environmentally mediated variation. We reasoned that a systematic analysis encompassing published compositional data generated under...