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Making crops taller, tastier, and more resistant to disease is a tedious process. For thousands of years, the only option farmers had was to pick two plants that showed particularly desirable characteristics and breed them together, hopefully creating offspring that shared those promising traits and avoided undesirable ones.

Modern gene-mutating techniques sped up this process. First, researchers worked out that by bombarding embryonic cells with radiation, they could force mutations in plant genomes, causing desirable traits to occur at random. They could then pull out these mutated cells and use them to generate entirely new plant lines.


In 2012, the geneticists Emmanuelle Charpentier and Jennifer Doudna found a much more precise way of changing a plant's genome. CRISPR-Cas9 is a kind of molecular pair of scissors that can be guided to a precise point in an organism's genome to chop out a troublesome gene, or insert a desirable one. In the agricultural world, CRISPR is already being used to create non-browning mushrooms, easy to harvest tomatoes and bananas that are resistant to certain diseases.

CRISPR is much faster and more precise than the selective breeding techniques used a hundred years ago. But the process requires a number of intricate steps. First, embryonic plant cells must be exposed to the CRISPR-Cas9 molecule so the editing can take place. Only a tiny percentage of them will be edited, and those lucky cells must be grown into full-sized plants which then – if everything goes to plan - will show the desirable trait that the researchers were trying to code for and hopefully produce seeds or clones that also carry that trait. It's a long process that requires multiple generations of plants and exhaustive testing and experimentation at every stage.

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But the US Defense Advanced Research Project Agency (Darpa), a government agency responsible for developing new technology usually for use by the military, wants to speed up this process. The agency is funding trials that, if they are successful, will mean that insects can be used to deliver genome-editing molecules to crops growing in the field. The research program, which is already underway in four different trials in the US, is now attracting consternation from biologists and ethicists who argue that this new technology poses a biosafety risk and could easily be turned into a new kind of biological weapon. It's all part of a program called "Insect Allies" that over four years will provide $47 million (£36m) in funding to research groups trying to develop a way of using insect-delivered viruses to edit crops in the field.

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This is how this technology would work. Say you're a farmer who just heard that next month there's going to be a plague of locusts that love munching the particular variety of maize you're growing in your field. You've already planted your maize, so there’s no time to grab some locust-resistant seeds and plant a new crop. Instead, you buy a whole load of aphids that have been infected with a genetically-modified virus programmed to insert a locust-resistance gene into maize plants. When those aphids start chomping on your maize plants, they'll transmit that genetically-modified virus to the crop. Once inside, the virus will release its gene-editing molecules and, if everything goes to plan, turn your normal maize plant into a locust-resistant maize plant.

So what was, a week or so ago, a field of ordinary maize plants, can become a field of locust-resistant maize plants almost as quickly as you can tug the lid off of your box of aphids. And if next week the weather report comes in and forecasts a drought? Then you reach for your box of aphids infected with a genetically-modified virus that carries a drought-resistance gene instead. That's the theroy, at lesat.

This, says Guy Reeves, a biologist at the Max Planck institute for Evolutionary Biology, would be a radical and worrying leap forward in biotechnology. "They are almost instantaneous and they are extremely flexible," he says. Even putting the insects to one side for a moment – something he says is "virtually inexplicable from every angle" – Reeves argues that there is real potential that this technology could be abused.

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"When you look at every single step to make it agricultural, rather than a weapon, it's always easier to make it a weapon," he says. Reeves and his colleagues set out their concerns surrounding this Darpa program in an argument published in the academic journal Science.


"To break something, to knock something out, is much easier than to gain a function," Reeves says. In other words, while the Darpa program is intended to deliver useful plant traits to a target crops, Reeves argues that the same technology could much more easily be used to surreptitiously damage or kill a crop. Imagine you were the despotic leader of a nation state that wanted to damage the crops of a far-off enemy. You could order the release of leafhoppers that carried a genetically-modified virus that, when transmitted to the plant, knocked out genes that were essential for plant reproduction, making its seeds sterile. "Is only when [they] planted those seeds next year that [they] would see there was a problem," Reeves says.

There are also major questions concerning how this technology might actually be usefully deployed in agriculture, although the program does include some safeguards to prevent anything going awry. Darpa is mandating that these trials take place in greenhouses, to minimise the risk of any insects containing genetically-modified viruses flying anywhere they shouldn't. They also require that by phase two (which ends at the start 2020) any trials incorporate "lethal safeguards" that ensure that insects can’t breed or survive longer than two weeks after release.

But Reeves can still see major problems if this technology was ever to make it to fields. For a start, gene-editing via an insect is fairly imprecise. It would be very difficult to prevent any insects from flying off and accidentally carrying the genetically-modified virus to other plants (most plant viruses and insects, Reeves notes, target many different crops). And even within the target field, it's very unlikely that every plant would be edited in the same way. In some plants, the edit might fail altogether while in others it might impact a different part of the genome. Most countries, particularly in the EU, have strict laws that govern the labelling and production of gene-edited crops. How would regulators deal with a field of maize that might contain some edited plants, some unedited plants and others that were edited in some unknown way?

Blake Bextine, the Darpa program manager running the Insect Allies program, says the agency has been in consultation with regulators since the program was first devised. “We’ve been in contact with regulators all along,” he says, including the US Department of Agriculture, the Environmental Protection Agency and the Food and Drugs Administration. All the facilities being used by the four academic teams working on the project have been inspected and certified by the USDA, he says.

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For the authors of the Science paper these aren't just technical hurdles that have to be overcome. The lack of discussion over these practical impediments, they argue, might mean that the program is perceived as an effort to develop biological agents for hostile purposes. If this is true, the authors argue, then the program would be in breach of the 1972 Biological Weapons Convention (BWC). The BWC prohibits the development of biological agents "of types and in quantities that have no justification for prophylactic, protective or other peaceful purposes."

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One concern, says Silja Voeneky, a law professor at the University of Freiburg and co-author of the Science article, is that is that the Insect Allies program as it stands falls into a grey area. Without plausible evidence that the technology is most useful for peaceful purposes, then there is, the paper suggests, a danger that the program would fall foul of the BWC. More transparent public discussions around this program, the technology involved and its potential implementations, the authors suggest, would go a long way to assuaging this uncertainty.

Bextine’s response is simple. “We are not developing biological weapons,” he says. “[With] any technology that is revolutionary, you can always point out parts that have dual use capabilities.”

The first phase of the four-year-long project has just wrapped up, and Bextine says that the teams have already shown that it’s possible to insert genes into growing crops using insects. Later phases of the trial will test whether one insect species can still accurately and safely deliver the genetically-modified virus in a greenhouse filled with many different crops and insect species – conditions that are much closer to the real world.

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But why not stick with existing gene-editing technology? The answer, Bextine says, is all about efficiency. Locust-resistant maize, for example, might grow a little shorter and slower than non-resistant varieties because it devotes some of its energy towards producing proteins that enable it to withstand and ward off bugs. If farmers could use insect-delivered viruses to ‘switch on’ resistance in maize plants, it’d mean that the plants could be super-efficient for most of the time, and only give up that efficient edge when they absolutely have to switch into locust-resisting mode.

And according to Bextine, helping crops withstand new threats on the fly is what Insect Allies is all about. “Food security is national security,” he says. “We want to secure our food supply.”

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