Detecting gene flow from GM crops

The likelihood of transgene movement into wild relatives of cultivated crops varies vary dramatically with geography. From the perspective of the UK, crops such as maize lack any close relatives and so effectively cannot act as a source for transgene recruitment into wild plant species. At the other extreme, forage grasses such as Lolium perenne are wind pollinated and have abundant wild populations growing in close proximity. In cases like this, hybrids will be so numerous and widespread that the risk assessment process should focus on the ecological consequences of transgene presence. In both of these scenarios, hybridisation rates have little importance in the overall risk assessment process. This is not the situation for the many crops that fall into the intermediate condition, where there are partially compatible wild relatives that only occasionally co-occur with the crop. In these instances, the extent of gene flow (initial hybrid formation) forms an important component of risk evaluation.