Hybridisation and introgression between crops and wild relatives

Gene flow from genetically modified (GM) crops to their wild relatives or to other, conventional crops has recently raised concerns among both scientists and the general public. It underlined that the potential negative effects of the use of genetically engineered crops could perhaps outweigh the potential agronomic benefits of their introduction. Examples of such negative effects – or ‘risks’ – concern: (i) Establishment of the crop as a new weed, both in natural and agricultural environments; (ii) Formation of “superweeds” by hybridization of a (wild/weedy) species with the transgenic crop; (iii) harm to non-target species; (iv) disruptive effects on biotic communities; and (v) genetic erosion (loss of original diversity of wild relatives). This study presents an overview of the current literature on the frequency and consequences of gene flow from crops to their wild relatives. The goal is to assess how this may help us to adequately perform Risk Assessment (RA) and monitoring procedures for GM crops, and also to identify in what areas more research is needed. In the debate on GM plants, “risk” is seen as a function of the effect of an event and the likelihood of the event occurring. Thus, the total risk depends on the probability of gene flow, and – once taken place – its effect on the recipient taxon and its environment.