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Plant Science Panel

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'The Ugly Truth'

by Tracey Brown, director of Sense About Science

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Cross pollination

Wendy HarwoodHuw Jones

Dr Wendy Harwood and Professor Huw Jones answered your questions on cross pollination and GM on Friday 4th May 2012. Find out more about Wendy and Huw 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’s the problem with doing this [GM wheat trial] research in a green house [as opposed to a field]?"

Huw Jones: We have done tests in a glasshouse and the results were spectacular; aphids were repelled and natural enemies attracted to our GM plants. However, people would be right to say this is does not reflect real life agriculture.

Wendy Harwood: A greenhouse can never replicate the range of environmental conditions found in the field. This means that field experiments are essential to really test how the wheat performs.

2.  "Why do you say insects can't carry off the GM wheat pollen?"

WH: Insects do not pollinate wheat so wheat pollen will not be carried off by pollinating insects. If pollen was ‘carried off’ it is only viable for a very short time (a few minutes) so would not be a problem.

HJ: Wheat is not insect-pollinated. Wheat flowers fertilise themselves before they open. Excess pollen, which is heavy and lives for only a few hours, then falls to the ground around the plant.

3.  "How does a small fence stop animals and birds spreading dangerous GM pollen and seeds?"

HJ: Pollen is not a problem, however, there is a potential hazard of birds or animals picking up seeds, either at time of sowing or around harvest time. Small mammals are excluded for the whole trial period by the fence which has small mesh (around 1cm). Birds are actively excluded for a month after sowing and at harvest time by management practices including bird kites, gas guns and tape.

WH: The trial has a variety of measures in place to deter birds and animals.

@orchid_b 4. "Genes jump, what’s to stop them jumping again?"  

WH: There are no wild relatives of wheat that it could cross with out in the field so genes could not ‘jump’ to other plants in this way. The risk assessment carried out will have considered whether the introduced gene could cause any harm in the environment if it spread. The trial would not have been allowed if there was a risk.

HJ: Nothing. The movement of genes from one type of organism to another via non-sexual means (so-called ‘horizontal gene transfer’) is extremely rare but it does occur naturally and is nothing specifically to do with GMOs.

5.  "Are you going to feed potentially contaminated wheat in nearby fields to rats to test its safety?"

HJ: No, and this suggestion is outrageous. There will be no contaminated wheat in nearby fields and there are simply no risks in our field experiment that justify the use of any animal experimentation.

WH: Pollen from the trial is extremely unlikely to be able to spread to nearby wheat fields. Rat feeding trials would not therefore provide useful information and the gene used in this wheat is already found naturally in other plants.

6.  "Do gas guns harm birds?"

HJ: Gas guns merely make a loud bang to scare birds away. They are powered by gas but perhaps the name is a little misleading!

7.  "In Guardian letters today Eddie Dougall says "birds and insects will carry GM pollen miles and wind will carry it hundreds of miles, with the inevitable effect of contaminating non-GM wheat." You can't control that. Why isn't the experiment being carried out under laboratory conditions?"

WH: If wheat pollen is carried by birds, insects, or the wind it will not be a problem as it is only viable for a few minutes so would not be able to pollinate non-GM wheat a long distance away.

HJ: These risks were considered by an independent panel of experts on the ACRE committee. Birds and insects do not collect wheat pollen. High winds at the time of flowering could in theory spread pollen but wheat pollen is heavy and lives for only a few hours. Combined with the self-pollinating nature of wheat and the absence of wild relatives, the risk of outcrossing was considered effectively zero.

8. "In the US, modified genes have transferred into local wildplants creating 'superweeds' which are resistant to herbicides. Farmers are now having to use stronger banned weed killers, as they are the only ones effective against the new weeds. Won’t this happen here?"

HJ: Wheat is 99% self-pollinating and it is a real challenge to make wheat-to-wheat hybrids, let alone cross wheat to something else. The only wild plant theoretically capable of crossing to wheat in the UK is couch grass. There have been some lab experiments that have made hybrids between wheat and couch grass but this needs man’s help and has never been seen in the wild. However, as part of the conditions of the consent, we will ensure no couch grass grows in our trial or in the surrounding 20m.

9.  "By growing wheat outside they have already put the seeds into the environment. So what would happen if it was found to be toxic? You can't unpollinate plants!!!"

WH: The gene used in this wheat is already found naturally in other plants so is already in the environment. Also wheat is mainly self pollinated and there are no wild plants that could be pollinated by it.

10. "You said insects don’t pollinate wheat but surely they land on the flowers?"

WH: In wheat the male and female parts of the flower are enclosed when pollination occurs. Therefore even if an insect landed on a wheat flower the pollen it might pick up would probably be old and not-viable.

HJ: Can I add, insects are not attracted to wheat flowers because they do not make nectar or scent. I’ve never seen a pollinating insect on a wheat flower.

Brendan Armstrong 11. "If modified genes from the experiment get into other crops what are the chances that these genes will mutate into something harmful, and how long would it take in years?"

WH: The genes introduced into the wheat could not get into other crops as wheat cannot cross with other crops or any wild plants to transfer the genes. The genes are no more likely to mutate than any other genes.

12.  "What about the concerns around the use of antibiotic resistant marker genes?"

HJ: The antibiotic resistance (ab) genes were used as part of the experimental procedure and are non-functional in the final plant. People are concerned about these genes somehow jumping from the plant into bacteria in the soil to make antibiotic resistant bacteria. Genes can jump like this in nature but is extremely rare. The ab genes used in these plants came from bacteria anyway and there are lots of soil bacteria with ab genes. This potential risk was considered negligible by the group of independent ACRE scientists.

13.  "Perhaps, if successful, the crop will negate the need for added chemical pesticide (a good thing). But then again, if the plants repel aphids there will be no aphids, and no insects eating the aphids, and no birds eating the insects, and no food chain. What if this research kills off all the aphids?"

WH: Even if this wheat was eventually grown commercially it would only repel aphids not kill them all. It would also attract natural predators of aphids. However, the possible effect on the food chain is something that would need to be considered if it was ever to be commercialised.

14.  "Someone said the wheat pollen dies very quickly. What does that mean? I didn't know pollen could die."

WH: What we mean is that the pollen would no longer be able to pollinate another wheat plant after a short period of time as it would be ‘non-viable’. Pollen is ‘viable’ for only a short period of time after being released from the anthers.

@eskoala 15. "What are the potential benefits of the research?"

HJ: Less pesticide use and more biodiversity. Aphids (green- and blackfly) are major pests that are normally controlled by spraying insecticides which kill them but also other beneficial insects. Our wheat plants control aphids by ‘scaring them off’ using an natural alarm pheromone normally made by aphids when they are attacked. Other insects are not affected. We know this works in the lab and think the aphids in our experiment will retreat to the wild flowers in hedges and field margins but we need to test this in the field.

Jeroen Crappé 16. "Re: Question 8 Is it really the herbicide resistance gene that is transfered to wild plants? Or is it in fact the overuse of glyphosate that enables those wild plants to become resistant via evolution?"

HJ: It’s a bit of both. If a herbicide resistance gene did transfer from a GM crop to a wild relative, that wild plant would also be able to tolerate that particular herbicide. A farmer would need to use another type of herbicide to kill it. It is also true that constant use of one type of herbicide on any (non GM) plant species will eventually generate resistant plants through the selection of random mutations.

17.  "The researchers say this gene is naturally in 100s of other plants. Does it spread from them to our gardens?"

WH: This gene may already be in many gardens as it is found in mint. The gene would only spread between plants able to cross-pollinate.

@westcoastcomms 18. "What is the widest held misconception about GM research?"

HJ: That it's somehow all controlled by big multinational companies. Most GM research is done in universities or by independent institutes to investigate the function of genes and to test ideas about how to make agriculture more efficient and sustainable in a world that needs more food from less land with less chemical inputs. GM is only one of the ways this can be done but we must not stop doing the research!

WH: Very interesting question. There are many misconceptions, maybe the widest is that GM technology is very very different to the methods used by plant breeders over the years. In fact plant breeders have widely used chemical and radiation treatments to deliberately induce changes to the DNA of plants so that they have more variation from which to select useful characteristics. GM can be considered just another method to provide additional useful variation to help address some of the future demands on our crop plants.



Our Q&As answer the questions people put, which may mean that some parts of a subject are covered well and others not. If there is an issue that you think is not tackled, you are welcome to send a follow up question to our plant science panel