The co-existence between transgenic and non-transgenic maize in the European Union: a focus on pollen flow and cross-fertilization

The ongoing discussion on the co-existence between genetically modified (GM) and non-GM crops becomes more important in the European Union (EU). With the recent inscription of 17 GM maize varieties in the common EU catalogue of varieties of agricultural plant species, the acreage of transgenic maize for market purposes is expected to increase in some European countries. In the EU, specific tolerance thresholds have been established for the adventitious and technically unavoidable presence of GM material in non-GM produce, and member states are elaborating legal frames to cope with co-existence. As maize is a cross-pollinated crop relying on wind for the dispersal of its pollen, technical management measures will be imposed to reduce cross-fertilization between transgenic and non-transgenic maize. Various biological, physical and analytical parameters have been identified to play a role in the study of cross-fertilization in maize. This variability may hamper the comparison between research results and may complicate the definition of appropriate isolation distances and/or pollen barriers in order to limit out-crossing. The present review addresses these parameters and proposes containment measures in order to not exceed the legal labeling thresholds in maize.