Letting the gene out of the bottle: the population genetics of genetically modified crops

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Abstract
Summary: Genetically modified (GM) plants are rapidly becoming a common feature of modern agriculture. This transition to engineered crops has been driven by a variety of potential benefits, both economic and ecological. The increase in the use of GM crops has, however, been accompanied by growing concerns regarding their potential impact on the environment. Here, we focus on the escape of transgenes from cultivation via crop × wild hybridization. We begin by reviewing the literature on natural hybridization, with particular reference to gene flow between crop plants and their wild relatives. We further show that natural selection, and not the overall rate of gene flow, is the most important factor governing the spread of favorable alleles. Hence, much of this review focuses on the likely effects of transgenes once they escape. Finally, we consider strategies for transgene containment. Contents Summary 429 I. Introduction 429 II. How do transgenes escape? – Hybridization, gene flow, and introgression 432 III. Assessing selection on transgenes – costs and benefits 434 IV. The effects of transgenes – case studies 435 V. Can we prevent transgene escape? 437 VI. Conclusions and future directions 440 Acknowledgements 440 References 440