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Plant Science Panel

Insecticides, biofuels, GMOs …

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'The Ugly Truth'

by Tracey Brown, director of Sense About Science

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GM trials, super-weeds, and ecosystems

Wendy Harwood Toby Bruce

Dr Toby Bruce and Dr Wendy Harwood answered your questions on GM trials, super-weeds, and ecosystems on Tuesday 17th July 2012. Find out more about Toby and Wendy here. This discussion was also tweeted about under #dontdestroyresearch.

If you have a question on a plant science related issue then get in contact with our Plant Science Expert Panel via Twitter, @senseaboutsci using #plantsci, or email us at [email protected].


1. What can we do to prevent ‘super-weed’s e.g. a GM crop with insecticide/ anti-frost etc. genes that spreads like a weed and potentially interacts with wild crops?

WH: Most crop plants grow well under agricultural conditions but do not cause problems as weeds. Good agricultural management should prevent ‘super-weeds’. In deciding whether a particular GM crop should be grown in a particular location, the risk assessment would look at whether there were any wild species that could potentially cross with the GM crop. If there were, then the risk assessment would look at whether spread of the new gene to wild plants would cause a problem. Decisions on where to grow GM crops need to be made on a case by case basis.

2. Could a super-weed cause problems in our eco-system? If so, what plan would be put in place to ensure they do not spread?

TB: By super-weed I assume you mean one which is herbicide tolerant and this could cause problems in agricultural ecosystems where herbicide is used. The best way to avoid this would be to minimise the use of herbicide to reduce the selection pressure for such weeds to evolve. In natural habitats where herbicide is not used then herbicide tolerance would not be expected to confer an advantage in competing with natural vegetation.

3. If ‘super-crops’ are created, i.e. crops that have an assorted variety of added genes from various organisms, would health risks increase? Would we create these?

WH: Some GM crops already contain several different added genes. This in itself does not increase health risks. The important thing is not how many genes are added, but what the effect of each genes is. When multiple genes are added, each gene product will be assessed for risk individually and any possible interaction between the genes would be considered. In the future, it is likely that we will need to create crops with more added genes so that they have a number of different advantageous characteristics.

4. Do GM crop trials occur over many seasons? If so, how many and would this be sufficiently long to look at potential dangers?

TB: The current GM trial of aphid repellent wheat at Rothamsted is being conducted over two seasons. It is a small scale trial and the main focus is on assessing if aphid populations are reduced under field conditions. The gene product is very widely occurring in nature and has a non-toxic effect even on the aphids. If the treatment works against aphids then further development may occur but it is too early to say at this stage.

5. Is the scale of the Rothamsted wheat trial sufficient to look at potential dangers?

TB: Our trial consists of eight 6m x 6m GM plots and eight 6m x 6m non-GM comparison plots. The scale is limited by the high cost of security for such trials but should be sufficient to obtain the information we require.

6. Can the sudden introduction of a novel species that has been manipulated by humans unbalance our current ecosystem?

TB: This question implies that genetic change is inherently risky. However, genetic change occurs via random mutations in nature. In some ways the effects of GM are more predictable because the change being made is known and a risk assessment can be made. Crops developed through mutagenesis screening, where crop seeds are exposed to high doses of radiation to induce unknown changes, have been grown for many decades and are even included in organic farming systems. If crops developed by mutagenesis have not unbalanced the ecosystem it is unlikely that GM crops will.

7. At the level of an ecosystem, what effect would the introduction of GM specie/s have? Would the new species be the equivalent of a new ecosystem?

TB: At the ecosystem level the change would not be large at all. A new ecosystem would involve a much bigger change than one gene in one species. To put it in perspective, our GM plants are only 0.00005% different from the wheat they were derived from. Genetic changes made during conventional breeding would be bigger than this and other agronomic changes would have more of an impact at the ecosystem level.



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