Several recent scientific studies examine the potential of transgenic plants to spread in the environment. In one of these studies, Chinese scientists demonstrate for the first time that outcrossing of glyphosate-tolerant genetically engineered (GE) rice into wild rice gives the hybrids a significant and long-lasting fitness advantage. Further studies examining soybean and oilseed rape and turnip have also added new evidence in regard to environmental risk.
Genetically engineered plants with glyphosate tolerance continue to dominate the global market. Transgenic oilseed rape, soybean, maize and cotton tolerant to the total herbicide are grown on well over 150 million hectares worldwide.
Chinese scientists recently published a study examining hybrids of glyphosate-tolerant GE rice crossed with wild rice over several generations. The results showed that hybrid offspring of the third to fifth generations exhibited considerable overall fitness advantages without the use of glyphosate, including plant height, number of panicles and grains per plant. The transgene conferring resistance to glyphosate was stably inherited and consequently led to changes in the plants’ metabolism, which in turn had a positive effect on the aforementioned fitness traits. This could be attributed, for example, to the fact that the additional EPSPS enzyme improves the biosynthetic pathways for certain amino acids. In contrast, the use of glyphosate is irrelevant here.
A similar recent experiment also shows that the backcrossing of genetically modified plants with wild species poses environmental risks. Here, scientists investigated the effects observed in subsequent generations of hybrids derived from glyphosate-tolerant GE soybean and wild soybean, although no glyphosate was applied. They initially found that resistance to glyphosate remained stable over four generations. In addition, hybrids with pronounced fitness advantages emerged. It appears that the spread of the transgenes can also benefit from the biological characteristics of wild soybean, which exhibits a vine-like growth habit. In fact, after several generations, some of the lines studied exhibited growth forms similar to wild soybean. According to the authors, such plants pose a significant ecological risk, as they could escape into the environment, where the transgenes could persist in wild populations and potentially even displace them.
A third recent publication examines the uncontrolled spread of transgenic, glyphosate-tolerant turnip in Argentina. Turnip (Brassica rapa), which can occur both as cultivated plant and as weed, is related to oilseed rape and can hybridise with it. Although herbicide tolerant GE turnip is not authorised anywhere in the world, such plants are spreading in Argentina and, according to the study, can now be found on an area of one million hectares. The researchers therefore investigated the origin of these plants. They found that they are most probably the result of cross-pollination with herbicide-tolerant GE oilseed rape. Transgenic, glyphosate-tolerant oilseed rape plants were first discovered in Argentina as early as 2012. This was surprising, as the cultivation of GE oilseed rape was banned in 1997. However, it appears that illegal cultivation is still widespread, which has led to the spread of the transgenic trait in the related plant species (turnip). As the plants are resistant to glyphosate, the frequent use of the herbicide in Argentina may have contributed to the spread increasing to this extent. Outcrossing of GE oilseed rape to wild turnip was previously also found in Canada.
All three studies demonstrate once again that ecological and genetic relationships are extremely complex and unpredictable, and that the negative consequences of growing genetically modified crops may only become apparent after many years.
Contact:
Christoph Then, Tel + 49 (0)151 54638040, info@testbiotech.org
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