Pollen dispersal and outcrossing from GM rape to conventional rape
Oilseed rape pollen can be transported over large distances by wind and insects, but this does not necessarily result in high outcrossing rates.
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This is because rape is largely self-fertilising. Even with direct contact, cross-fertilisation only occurs in around 30 percent of cases.
If genetically modified rape is grown, coexistence with conventional rape crops must be ensured. For oilseed rape, as for other crops, adventitious and technically unavoidable GMO contamination of the harvested product below the 0.9 percent threshold is permitted without labelling, provided that the GM rape in question is licensed in the EU.
It is not only the outcrossing rates that have to be considered to ensure coexistence: "Volunteer" rape could be a particular problem. If GM rape plants germinate in subsequent years, their seeds could spread through a conventional crop.
Trials and studies focusing on coexistence in GM oilseed rape cultivation
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Research projects: summary of resultsTopic: Outcrossing from GM rape to neighbouring conventional rape fields Result (1): Two GM rape varieties with different herbicide resistances were grown in adjacent plots and surrounded by a cordon of non-transgenic rape. GMO inputs declined sharply in all directions as distance increased and were on average below 0.1 percent at a distance of 50 metres, regardless of the wind direction. A ten metre wide open space between the different rape plots significantly reduced incrossing in plants on the inner edge of the cordon. Result (2): The pollen count fell appreciably as distance increased. Outcrossing to adjacent non-transgenic plots was below 0.3 percent on average. The threshold of 0.9 percent can be complied with even in directly adjacent fields. The outcrossing results were independent of the wind direction in this trial year. Result (3): Outcrossings to adjacent rape fields are generally below 0.9 percent even a short distance away. Lower outcrossing rates were detected up to a distance of 26 metres from the source.
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Topic: Pollen dispersal by wind and flower-visiting insects Results: At a distance of 10 metres from the oilseed rape field, only around 4.5 percent to a maximum 37 percent of the amount of pollen measured at the field margin is still present. Insects in particular are responsible for carrying the pollen over large distances. The bumblebee has a radius of up to two kilometres, and the honeybee from five to fourteen kilometres. |
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