Traceability of genetically modified organisms.

EU regulations stipulate the labeling of food products containing genetically modified organisms (GMOs) unless the GMO content is due to adventitious and unintended 'contamination' and not exceeding the 1% level at ingredient basis. In addition, member states have to ensure full traceability at all stages of the placing on the market of GMOs. Both requirements ensure consumers 'right to know', facilitate enforcement of regulatory requirements and are of importance for environmental monitoring and postmarket surveillance. Besides administrative procedures, such as used in quality certification systems, the significance of adequate molecular methods becomes more and more apparent. During the last decade a considerable number of molecular methods have been developed and validated that enable the detection, identification and quantification of GMO impurities. Most of them rely on the PCR technology and can only detect one specific stretch of DNA. It can, however, be anticipated that in the near future the situation will become more complex. The number of GMO varieties, including 'stacked-gene' varieties, which will enter the European Market will increase and it is likely that these varieties will harbor more variable constructs. New tools will be necessary to keep up with these developments. One of the most promising techniques is microarray analysis. This technique enables the screening for a large number of different GMOs within a single experiment.