Glyphosate-resistant weed on the rise
21 September 2022 / In Canada, cross-pollination of genetically engineered oilseed rape into a related weed species has occurred, and the weed is now spreading in the fields. This was revealed in a recent study by Canadian scientists. The spread of the plants challenges previous assumptions about their safety.
Farmers from the Quebec region had noticed that rapeseed-like plants resistant to the herbicide glyphosate were spreading in their fields. Molecular tests subsequently showed that some of the plants were indeed genetically engineered, herbicide-tolerant oilseed rape. Such plants have been grown on a large scale in Canada for about 25 years, and currently covers around 8.6 million hectares. The findings in the Quebec fields were nevertheless surprising, as the farmers involved had never grown oilseed rape before and there is also hardly any oilseed rape cultivation in the entire region.
Even more surprising, however, was a second finding of the study. A part of the plants resistant to glyphosate belonged to the species Brassica rapa (bird rape mustard), which is closely related to oilseed rape and occurs as a weed in many regions. Oilseed rape and B. rapa are intercrossable, hybrids of genetically engineered (GE) oilseed rape and bird rape mustard have already been detected along transportation routes and near ports in countries that import GE oilseed rape. However, scientists assumed that the hybrid plants had reduced fertility and were therefore unable to establish in the environment permanently. In contrast, the current study shows that the genetically engineered trait is now detectable in purebred and weedy B. rapa plants in Canada, presumably through multiple backcrosses of the hybrids.
Further, a third discovery surprised the researchers: amongst the plants studied were crosses of GE oilseed rape and field radish (), another wild relative of oilseed rape with weedy characteristics. Although the two species had already been crossed with each other in the laboratory, this would likely be the first proven case of hybridisation under natural conditions, according to the scientists.
Since large parts of Canadian agriculture are based on glyphosate-resistant GE crops such as maize, canola and soy, the GE bird rape mustard plants have an important fitness advantage and find excellent conditions for propagation. In addition, there have been various studies in recent years that have shown that plants made resistant to glyphosate by genetic engineering can exhibit unexpected biological effects. These give the genetically engineered plants a survival advantage even if no glyphosate is sprayed at all.
In the study, the authors express overall concern that genetically engineered traits of crops such as rapeseed can cross out into related weeds and point out that weed traits of potential crossing partners should be considered before introducing GM crops.
In particular, GE oilseed rape has proven to be a particularly problematic crop, as a recent review study also shows, and is now spreading uncontrollably in numerous countries around the world. Testbiotech has long advocated that the release of GE crops should be prohibited if their spread in the environment cannot be controlled in the spatio-temporal dimension .
The present study once again demonstrates the complexity and unpredictability of ecological relationships. Against this background, Testbiotech also warns against plans to deregulate plants derived from new genetic engineering (genome editing).
Christoph Then, Tel + 49 (0)151 54638040, email@example.com