Aphids (also known as greenfly and blackfly) are unwelcome visitors that suck sap from plants. They cause significant damage to agriculture and reduce farmers' yields by damaging crops and spreading plant diseases.
Wheat is the most important UK crop with an annual value of about £1.2 billion. Currently a large proportion of UK wheat is treated with broad spectrum chemical insecticides to control cereal aphids that reduce yields by sucking sap from plants and by transmitting barley yellow dwarf virus. Unfortunately, repeated use of insecticides often leads to resistant aphids and kills other non-target insect species including the natural enemies of aphids, which could have a further impact on biodiversity.
Scientists at Rothamsted, funded by the UK Government through the Biotechnology and Biological Sciences Research (BBSRC) have been seeking novel ecological solutions to overcome this problem in wheat. One approach has been to use an odour, or alarm pheromone, which aphids produce to alert one another to danger. This odour, (E)-β-farnesene, is also produced by some plants as a natural defence mechanism and not only repels aphids but also attracts the natural enemies of aphids, e.g. ladybirds. Our scientists are using biotechnological tools to genetically engineer a wheat plant which produces high levels of this aphid repelling odour, which could help promote sustainable and environmentally friendly agriculture.
This work is sponsored by the BBSRC and not a commercial organisation, nor for commercial gain. It forms part of a wider scientific strategy for Rothamsted Research to meet the challenge of increasing food and energy production in a more environmentally sustainable way.
The history of the work
The work is the product of years of studying how insects naturally interact with one another and with the plants that surround them in the ecosystem through their natural chemistry. The decision to use genetic modification as a tool was after trying other approaches (synthetic dispensers and essential oils with high levels of (E)-β-farnesene) that did not provide effective delivery of the repellent odour. Release of the repellent from the plant will improve the performance of the repellent as done by the wild potato. Our innovative approach to crop protection is based on an understanding of insect chemical ecology. Use of insect repellents and attractants delivered by crops has been used successfully in a push-pull companion cropping system in E. Africa which is a non-GM system. Our new GM project will test if it is possible to deliver semiochemicals from crops themselves instead of having to grow additional companion crops.
This clip shows aphids (Myzus persicae on Chinese cabbage) responding to alarm pheromone. A colony is on a leaf, a syringe delivers some alarm pheromone (you can just about see it at the start of the clip). After perceiving the alarm pheromone, the aphids become agitated and move away.
Questions and answers
Why wheat and why aphids?
With wheat being the most important UK crop, with an annual value of about £1.2 billion, no one should underestimate the potential economic consequences that insect pests, like aphids, can cause to UK farming community.
Last summer, anyone tending to their gardens was acutely aware of the damage aphids can cause to plants. For the UK wheat farming community the damage aphids cause to crops can devastate their livelihoods due to lower yields and reduced income. Aphids damage crops directly by sucking nutrients from plants and indirectly by spreading harmful plant viruses.
We believe the UK is in a position to be a world leader on wheat research. Wheat provides around 20% of human calories, but since 1980 the rate of increase in wheat yields has declined.
Why do we need to produce more food using fewer pesticides?
Even today over one billion people are still permanently hungry. The Chief Scientific Adviser for the UK described the world as heading for a "perfect storm" where demands for energy, water and food will increase dramatically with an underlying threat of climate change. Agriculture is in the eye of this perfect storm as it is (1) a producer of food, (2) both a producer and consumer of energy and (3) the world's biggest consumer of the fresh water. Agriculture also affects, and is affected by, climate change.
Around 25% of wheat crops can be lost through insect pests, pathogens and viruses (Oerke 2006). These are usually controlled with chemical sprays, but repeated use of these, for example pesticides, often leads to resistant strains and kills other non-target insect species including the natural enemies of pest, which could have a further impact on biodiversity. The process of producing and spraying pesticides may also have an inevitable environmental impact.
Whether this is a problem of politics, production or distribution is a complex issue, but as scientists we must responsibly explore all technologies at our disposal to help counteract this "perfect storm".
Rothamsted Research, being the longest running agricultural research station in the world, is therefore at the heart of meeting the challenge of increasing food and energy production in an environmentally sustainable way.
Health and safety questions
Is the trial safe?
Thorough risk assessments of this field trial were carried out by the Rothamsted GM Safety Committee and no major safety concern were raised.
Following this, the Government's ACRE (the Advisory Committee on Releases to the Environment) said it was "satisfied that all appropriate measures have been taken to avoid adverse effects to human health and the environment from the proposed release" in September 2011, which received coverage through local and national news channels.
ACRE is a statutory advisory committee appointed under section 124 of the Environmental Protection Act 1990 (the EPA) to provide advice to government regarding the release and marketing of genetically modified organisms (www.defra.gov.uk/acre/).
As part of the ACRE process, there was a 60 day public consultation period 20th June to 19th Aug 2011, with input from organisations, e.g. GM Freeze, and the Report stated that "ACRE is satisfied that all scientific issues raised by the public with respect to this application have been addressed".
There are three new proteins made by the GM plants [(E)-β-farnesene synthase, farnesyl pyrophosphate synthase and phosphinothricin acetyltransferase]. The first two are common proteins found in many organisms (some that are part of the food and feed chains). The third is a bacterial protein. All are non-toxic, non-allergenic and pose no safety concerns that we know of.
As part of the application process we have agreed that no wheat plants grown in the trial will be fed to humans or animals.
Can the genes move into surrounding areas?
The probability of seeds moving from the trial site or the transfer (via cross-pollination) of inserted characteristics to sexually-compatible species outside the trial area is estimated as very low. Wheat seeds and wheat pollen grains are relatively large and not normally dispersed by wind.
In addition, we have put in place strict management procedures to minimise the spread of seeds or pollen, which will further reduce the probability of these events occurring.
The GM plots will be separated from the edge of the trial by 10 meters of barley (or space) plus a 3 metre 'pollen barrier' of wheat that helps to contain pollen from the GM plants within the trial site. All these plants are treated as though they are GM and harvested /destroyed at the end of the trial. There will be no cereals grown for 20 metres outside the boundary of the site and no wild relatives of wheat that can cross with our cultivated variety exist in the vicinity.
Couch grass species, distant relatives of wheat will be controlled in a 20 metre wide area around the trial site to avoid any slight possibility of cross-pollination.
In addition to all this, the actual chances of successful establishment of these wheat plants outside the plot in the wild are extremely low as they are naturally not very competitive with other plants.
Might animals eat the seeds? What would happen to them?
It's possible that small mammals such as field mice could get in and eat the seeds. There is no chance that the genes could end up in the mouse population, the DNA would simply be digested and broken down into basic nutrients.
We will ensure that suitable measures are in place to keep pigeons and other large birds out of the trial site during and after sowing and at the first signs of emergence of wheat ears.
What is the impact on natural aphid predators?
One of the reasons for the trial is to assess the effects on other insects, particularly insect "predators" (e.g. ladybirds) and "parasitoids". We have shown that aphid parasitoids (small wasps that are natural parasites to the aphids) spend longer on (E)-β-farnesene pheromone releasing plants and olfactometer studies have shown they are also attracted to (E)-β-farnesene, as are ladybirds.
The overall effect of the EBF wheat is likely to be beneficial to these other insects, as they will not be killed as is currently the case when fields are sprayed with broad spectrum pesticides. But this is the point of the trial, to provide evidence to test this hypothesis.
What is the likely impact on non-GM farms as a result of displaced aphids?
The field trial will not have an effect on aphid populations on other farms. This is a very small scale experiment, with eight 6 metre x 6 metre plots.
Have you considered other ways to use the 'aphid alarm' system using non-GM techniques?
The Chemical Ecology group here at Rothamsted Research has over 30 years experience of studying natural attractants and repellents for controlling pests. Our studies show that the most effective way of doing this is by getting the plant to produce these attractants and repellents. Using GM as a tool is one way to achieve this.
We have already investigated using the (E)-β-farnesene chemical itself through spraying in pure form and in essential oils. We have found that it is unstable, which means that its effects vanish quickly, and it is difficult to formulate for sustained release. This is why release through the plant would be ideal.
In other projects we use natural insect repellents using non-GM approaches, for example in the push-pull system.
Wouldn't it be better to just introduce more ladybirds?
Unfortunately once the aphids are on the plants where they are eaten by ladybirds they often have already caused significant damage by spreading plant diseases. What we need is front line defence to ensure that the majority of them never reach the plants.
Our method could also increase the numbers of ladybirds and other predators because they are actually attracted to the smell of the pheromone, (E)-β-farnesene.
In addition, a reduction in use of broad-spectrum insecticides could also protect ladybirds from being harmed.
Does this mean that no chemicals will be used on wheat? Is the GM wheat organic?
If the experiment works in the field as it has done in the lab, this might mean that we wouldn't need to use chemical insecticides to control aphids, which would certainly reduce the amount of chemicals needed to grow wheat.
It doesn't necessarily mean that no chemicals would be required at all, just not the ones that we normally use for aphids.
The Rothamsted farm is not organic. We will use conventional farming practices including the application of fertilizer and other inputs. The wheat would only be organic if only chemicals approved by the soil association were used to grow it.
Where will the aphids go? Won't they just attack other plants?
Part of this experiment is to examine, in a real-life setting, how any changes in aphid behaviour interacts with other insect populations. For example, this will include how the experiment influences the behaviour of the aphids' natural predators such as ladybirds.
The aphids may disperse to areas of wild grasses where natural insect "predators" (e.g. ladybirds) and "parasitoids" (small wasps that are natural parasites to the aphids) would keep their populations in check. They would feed into food chains supporting wildlife such as birds in the countryside.
How did you make the GM plants?
We took small samples of wheat plants and physically inserted the genes into the cells. The genes to be inserted were coated onto the surface of very small particles of gold shot into wheat cells using a device that is sometimes called a "gene gun". We then used the cells containing the new genes to make seedlings in the lab.
We actually made lot of different transgenic plants using both the 'gene gun' and another method involving a soil bacterium Agrobacterium tumefaciens but the lines possessing the highest (E)-β-farnesene emission were plants made using the gene gun and these were chosen for the field trial.
Can you see any differences between normal wheat plants and the GM ones?
GM plants and control wheat plants look identical. They can be distinguished by techniques that compare the DNA they contain or by analysing the (E)-β-farnesene they give off.
Where did the genes come from?
The genes we inserted into the wheat plants were chemically synthesised and not taken from another plant or animal.The gene that makes (E)-β-farnesene, encodes a protein that is similar to that found in peppermint but versions of this gene are also present in many other plants. The other gene that is needed, the "farnesyl pyrophosphate synthase gene", is widespread in nature and can be found in most organisms.
We used synthetic genes which is a standard procedure for modern molecular biology. The synthetic form of the farnesyl pyrophosphate synthase gene we used encodes a protein that happens to be most similar to that found in cow but is not significantly different to the versions found in nearly all other organisms. It is not a cow gene, it just looks like one. A bit like two unrelated individuals who have an uncanny resemblance to each other.
Could the herbicide and antibiotic resistance genes end up in other organisms and cause problems?
Wheat is a self-pollinating plant. Wheat pollen is too heavy to travel far on the wind and lives for only a few hours so cross pollination is almost impossible.
Horizontal gene transfer from plants to soil bacteria is an extremely rare event but has been demonstrated to occur under certain 'artificial' conditions and we will be investigating the extent to which any genetic material from the plants persists in the soil. If this were to occur, it is extremely unlikely that a population of bacteria with these genes would be established. This is because there is no particular evolutionary benefit for soil bacteria to have them and they would soon disappear from the population of soil bacteria.
Will the inclusion of an antibiotic resistant marker gene contribute to a rise in resistant infections in humans and animals?
The transgene is fully integrated into the wheat DNA and it would be incredibly difficult for any parts of it to move into other organisms. No antibiotics will be applied to the soil so, even if some of the DNA were to transfer, there would be no selective advantage for those cells to reproduce and they would simply die out.
Why are you using Spring wheat?
Winter wheat would have been a better model for UK agriculture but this is an early stage experiment and 'spring type' wheat provides a more efficient experimental system to test our hypothesis, most notably it is easier to transform, has no vernalisation requirement and therefore the experiment can be conducted in a shorter time frame. Vernalisation is a process where seeds are subjected to low temperatures in order to speed up plant development and flowering. Our 'spring type' wheat, Cadenza, also has good frost-tolerance which will protect the experiment from our unpredictable UK weather.
Aren't you just doing this for commercial gain?
This combination of genes in this experiment will only be used for the trial and alternatives would need to be used in a commercial variety that is able to produce (E)-β-farnesene. So even if the emission of (E)-β-farnesene provides excellent protection from aphids at the field level (the trait under evaluation in these trials) and this approach looks promising then the transformation would need to be refined to produce a commercial variety.
By their very nature all new discoveries are commercially viable. As scientists though, our interest is about using scientific process to generate evidence to show if a technology works.
What will you do with the results? Who owns the results? Will you patent the idea?
The results will be freely available as soon as practicable after the experiments are completed. Data will published in peer-reviewed scientific journals and disseminated via other relevant media. The ideas have not been and cannot be patented due to the fact that we have previously discussed them in various publications.
Why don't you just jump straight to producing and testing a commercial crop?
We are not growing a commercial product, but instead conducting a scientific experiment. If the experiment gives us data suggesting that there may be viable environmental benefits to this type of genetic modification, then further experiments could be conducted to make a similar modification more like a commercial product.
To produce a commercially viable crop that can repel aphids and is fit for human consumption requires further experimentation and regulation, which is way down the road and not the main purpose of this specific experiment at this stage.
The logistics of the trial
Where is the GM trial?
The GM field trial is on the experimental farm at Rothamsted Research in Harpenden, an agricultural research establishment that receives strategic funding from the Government via the BBSRC (Biotechnology and Biological Sciences Research Council).
Rothamsted has many experimental plots covering the whole estate, of which this trial forms one very small part. Some of these experimental plots have been running continuously for nearly 170 years, helping to shape our knowledge of agriculture and ecology. These Long Term Experiments, a UK national capability funded by the BBSRC and Lawes Agricultural Trust, are unique and are precious. They still provide valuable data for current research at Rothamsted, as well as being an invaluable UK and international resource.
Can I come and look at it?
Yes, it's possible to see the trial but you will require permission from Rothamsted Research in order to do this.
The plot is surrounded by a perimeter fence that has been erected to prevent the entry of rabbits, other large mammals, and unauthorised people to ensure the experiment is conducted with the scientific rigour and high standards expected at Rothamsted Research.
There is a public footpath which runs about 50-80 metres from the fence and there will be information points around to inform members of the public what the trial is about.
How big is it?
There will be eight 6x6m plots (288m2) planted with GM wheat in 2012 and the same again in 2013. The total area including non-GM controls and spacing between GM plots will cover 80 x 80 metres. We propose to carry out two trials in consecutive seasons and to avoid reusing the same ground, which will give us more accurate results.
How long will it last for?
It will last for 5 or 6 months (from March/April - Aug/Sept depending on the weather) in 2012 and the equivalent time period again in 2013.
How much did it cost? Who is paying for it?
The field trial is part of a five-year project funded by the BBSRC. The value of the whole project is £732,000.
An additional £180,000 was provided by the BBSRC for security measures.
Planned protests on the Rothamsted Research site
We are aware that some individuals may wish to protest on our trial site and have written to the organisers to see if Rothamsted Research can be of assistance on, or leading up to, the planned day of peaceful action. We are committed to engaging people with a diversity of views around our work.
We would be pleased to provide a platform where representatives from their groups and Rothamsted could present their perspectives on this issue. Our scientists will also be on hand to listen to the protestors' concerns and to discuss the trial. We will also make ourselves available to speak to this group before the public day of action, if they wish.
Scientists at Rothamsted research have also made an independent video plea to protestors planning to "decontaminate" their scientific trial, instead asking them to enter into the spirit of dialogue and not a spirit of destruction.