Gene escape is seriously bad news

March 2022

In 2005 the scientific view was that "... the movement of transgenes beyond their intended destinations is a virtual certainty" (quoted in Ellstrand)

Gene escape from GM crops is something environmental activists have done a lot of shouting about. However, although regulatory lip-service is paid to it in risk assessments, the consequences of walk-about genes seem to be swept under the carpet. The biotech mindset is that artificial genes (including edited ones) will only do what they've been constructed to do wherever they end up: for example, herbicide-tolerance genes will be neutral in the absence of the herbicide, pesticide-generating genes specific to a target pest will be neutral in the absence of that pest, and anyway artificial genes won't find their way into a comfortable, alternative plant host often enough for it ever to matter.

In real-life, not all GM plants are growing neatly in fields [1] and, where wild relatives grow within pollinating distance of GM plants, gene-pollution of their weedy cousins has been widely reported. Although studies on the ecological consequences of this are thin on the ground, what little information we have is ominous.

Laboratory experiments on a commonly-used, well-characterised model plant, arabdopsis, found that the insertion of a gene for glyphosate herbicide-tolerance caused the plants to grow bigger, produce more seed and germinate better under stress [2]. Potentially, the perfect super-weed.

Even before the arabdopsis trial was published, tests on the effects of gene-flow from GM Asian cultivated rice into two wild rice species found that the transgene for glyphosate-tolerance conferred extensive fitness benefits, including increased branching of stems (bushier plants), earlier flowering (circumventing cold-stress), more seeds and enhanced over-winter survival. Rice superweeds are not good news.

One of the weedy rice species tested is a direct ancestor of Asian cultivated rice and an important germplasm for genetic improvement of rice crops. Genetic pollution of this valuable resource is seriously bad news.

Mexico has been growing GM cotton for 25 years. Although there's been plenty of time for native species to acquire transgenes and evolve within their natural habitats, the opportunities seem few: cotton is 90% self-pollinating and the crop-growing areas in the north do not overlap with the wild rice distribution in the south. It was, therefore, unexpected when, in a small sample of 61plants in an unspoilt coastal area, scientists found over a third had a glyphosate-tolerance gene, over ten percent had a Bt (insecticidal) gene, and fifteen percent had both artificial traits. The closest GM cotton crops were nearly 2000 kilometres away (To put this in perspective, the longest distance one can travel between two points in the UK is only 1352 kilometres). It seems there have been insufficient control measures in place in Mexico to prevent spillage of GM cotton seed during transport, made worse by the ease with which cotton seed can be dispersed by wind and water.

Further investigation of these GM-weed hybrids uncovered the extent of the ecosystem disruption they could cause.

The environmental parameter chosen for study was ants: the plant characteristic investigated was nectar production by the leaves. Nectar is exuded by the leaves of cotton plants in response to stress, such as an attack by a herbivore. It attracts ants which feed on the nutritious liquid and scare off the predators. Ants are, therefore, important to the cotton's successful survival and reproduction, but because they're not a target insect of the Bt in GM cotton they're assumed not to be affected by gene pollution.

Eight species of ant were found associated with the weedy cotton. However, not all ants are the same: some are aggressive to other insects, others are benign. With over 400 constituents in nectar, there's plenty of scope for artificial genes to disturb the quantity and nutrient profile of the secretion and attract the wrong kind of ant. Then, for example, too many aggressive ants could scare off pollinators as well as enemies, too many benign ants could fail to keep the herbivores away.

In the GM cotton weeds, glyphosate-tolerant genes were associated with low nectar production even when stressed, and extra benign ants, plus low but visible herbivore damage. Insecticide-generating genes in cotton weeds were associated with continuous nectar production in equivalent quantities to stressed wild-type cotton, and extra aggressive ants.

The study demonstrated that:

"the presence of (GM) genes can cause intrinsic changes in wild populations of cotton ... and changes in their ecological interactions." 

It also illustrated how far-reaching and complex the effects of gene pollution will be in natural ecosystems.

As one of the authors, Ana Wegier, remarked "what surprised (her) the most was how easy it was to
find changes where we didn't expect them". Such a high proportion of GM weeds in wild cotton populations nowhere near GM crops indicates just how inevitable gene pollution is.

Wegier said:

"We know the presence of transgenes is irreversible, and the (ecological) effects are irreversible". 

Mexico is a reservoir of cotton's genetic diversity: pollution of this valuable resource is seriously bad news.

Testbiotech commented on the potential scale of the risk even with the small variety of commercialised GM crops we have now:

"If gene flow to natural populations cannot be prevented, this can put biodiversity and the livelihoods of future generations at risk. These risks concern the cultivation of (GM) plants such as oilseed rape in the US, Canada and Australia, camelina in the US, rice in Asian countries and cowpeas in Africa. There is also a risk caused by import of (GM) plants for the EU if, for example, spillage occurs during transport from viable kernels of (GM) oilseed rape. Plants growing from these kernels can survive in the environment and spread uncontrollably".

OUR COMMENT

GM in a weedy genetic and ecological background is not substantially equivalent to its agricultural parent.

All the signs are that the herbicide-tolerance gene interferes in multiple biochemical pathways essential to the plant's balanced existence within a complex natural environment, while the Bt gene causes the plant continuous and damaging stress under all circumstances.

As GM Watch pointed out "The project provides strong evidence that contrary to what is claimed by industry, the risks of genetically engineered plants are not sufficiently investigated." Westminster is determined to rush down a GM agricultural path in the UK: bring the fact of inevitable, permanent gene pollution and environmental damage to the attention of your regulators.


Background

[1] ESCAPED GENES: A RISK ASSESSMENT MINEFIELD - March 2022

[2] SUPER-FIT GM WEEDS - June 2018


SOURCES:

• Normal C. Ellstrand, 2018, "Born to Run"? Not Necessarily: Species and Trait Bias in Persistent Free-Living Transgenic Plants, Frontiers in Bioengineering and Biotechnology 6
• Valeria Vázquez-Barrios, et al., 2021, Ongoing ecological and evolutionary consequences by the presence of transgenes in a wild cotton population, Nature Research
• Martha G. Rocha-Munive, et al., 2018, Evaluation of the Impact of Genetically Modified Cotton After 20 Years of Cultivation on Mexico, Frontiers in Bioengineering and Biotechnology 6
• Spreading the risks: When genetically engineered organisms go wild, GM Watch 4.03.20
• Wei Hu, et al., 2020, Genetic and evolution analysis of extrafloral nectary in cotton, Plant Biotechnology Journal 18
• Emiliano Rodríguez Mega, Modified genes can distort wild cotton's interactions with insects, www.sciencenews.org, 16.02.21

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