Genetically modified oilseed rape. Aspects in relation to the environmental risk assesment and post-market environmental monitoring of import applications

Brassica napus (oilseed rape) has the biological characteristics to cross-pollinate with wild relatives and to form feral populations under northern-western European climatic conditions. Spillage of B. napus seeds can therefore lead to the establishment of feral B. napus populations. These populations occur along transport routes such as roads and railways, and around previous cultivation sites. If a population arises from spilled herbicide tolerant genetically modified (GM) B. napus seeds, use of the corresponding herbicides provides a selective advantage for the GM plant.
B. napus can cross-hybridise with wild relatives, which may involve the permanent incorporation of transgenes in feral populations. Further cross-fertilisation can eventually lead to several transgenes coming together in one plant (stacking). In the literature, stacking of transgenes in B. napus has been reported along roadsides in North America which had been sprayed with herbicides. Interspecific hybridisation between B. napus and B. rapa (turnip) occurs under natural conditions and has been reported in the Netherlands. It is known that backcrosses between these hybrids and B. rapa may occur in the field.
The environmental risk assessments (ERAs) of the currently authorised GM B. napus events in the European Union indicate that these events in themselves do not pose a risk to the environment in the Netherlands. However, stacking of transgenes may occur in feral B. napus. It cannot be excluded that a possible combination of GM traits and/or a possible interaction between gene products, expressed by the genetic modification, may result in a potentially adverse effect. Therefore, general surveillance of feral GM B. napus populations will be needed to identify any unanticipated, delayed or (in)direct adverse effects. As these (stacked) GM B. napus plants are most likely to occur in handling areas and along transport routes, in particular when herbicides are used for weed control, general surveillance should focus on these areas. Where GM B. napus plants occur, transgene flow to B. rapa is possible. Any B. rapa populations in the vicinity of GM B. napus should therefore be included in the general surveillance plan and monitored for the presence of transgenes.