Genetically modified canola may lose genes when escaping into the wild

In a recent discovery that challenges previous assumptions, a study by Steven E. Travers, D. Bryan Bishop and Cynthia L. Sagers reveals that populations of canola genetically modified for herbicide resistance can survive off farms. However, these populations may be gradually losing their modified genes.

Traditionally, it was believed that genetically modified crop plants that escaped agricultural fields would be ephemeral. This would imply a lower probability of them dominating wild areas or transferring their inserted genes to wild populations of genetically close plants. However, few studies have been carried out to verify whether these canola populations could actually survive long-term in the wild.

The recent study involved extensive research into populations of genetically modified canola growing along roadsides in North Dakota, repeating an initial survey conducted in 2010. It was noted that the total number of modified canola plants in the sample had decreased and that the presence of these populations became less common over time. Additionally, when researchers tested plants for herbicide resistance, they noticed that the types of herbicides the plants were resistant to had changed over time, likely due to changes in the varieties planted by farmers. It is important to highlight that almost a quarter of the plants were not resistant and did not contain transgenes — an increase from 19,9% ​​in 2010 to 24,2% in 2021 — suggesting that these populations may be losing their transgenes.

The researchers hypothesized that populations of engineered canola may be under evolutionary pressure to eliminate transgenes, which could occur if the variety was at a disadvantage when it was no longer being grown on farms. Additional genetic analyzes could help clarify plant origins and provide more information about how long transgenes can persist in the environment.

Steven Travers commented: “The assumption that transgenic crop varieties would be restricted to benign agricultural field conditions and would not mix with natural plant populations can be discounted. Long-term self-sustaining feral populations of canola (some transgenic and some not) are a worldwide phenomenon and as such emphasize the need for more research into how dedomestication works, the extent to which it impacts natural populations, and the risks that the adventitious presence of transgenes may represent for agriculture.”

The researchers' article on the subject received the following summary:

“The generalization of genetically modified (GM) crops increases the risk that transgenes will be integrated into natural and naturalized plant populations. A fundamental assumption of managing genetically modified crops is that escaped plant populations are short-lived and therefore the risks they pose are limited. However, few escaped crop plant populations have been tracked long-term, so our understanding of their persistence in ruderal or natural landscapes is limited. We repeated a large-scale road survey of wild GE canola populations in North Dakota, USA, initially conducted in 2010. Our objectives in 2021 were to determine the current distribution of wild GE canola populations and establish the relative frequency of GE and non-GE canola. transgenic. GE phenotypes in canola populations across North Dakota. Our results indicate that although the incidence of wild canola was lower in 2021 than in 2010, escaped canola populations remain common throughout the state. The prevalence of alternative forms of resistance to GM herbicides has changed between surveys, and we have found an overabundance of non-GM plants compared to the frequency of non-GM forms in cultivation. Indirect evidence of persistence includes sampling plants with multiple transgenic traits and locating populations far from transport routes. We conclude that wild canola populations that express resistance to transgenic herbicides are established outside of cultivation, that they may be under selection for transgene loss, but that they still pose long-term risks by harboring transgenes in the unmanaged landscape.”

The complete material can be read at doi.org/10.1371/journal.pone.0295489