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The Advance of Designer Viruses in Agriculture


Combatting Disease

Scientists believe designer viruses created in the laboratory can help the agricultural industry deal with pathogens and extreme weather. A vast experiment is currently being planned. But can the viruses be controlled?

When the biologist Michael Irey was called out to a pomelo orchard on the outskirts of Miami in 2005, he had a feeling that a catastrophe was brewing. Irey, who worked for the U.S. Department of Agriculture at the time, had been sent out to confirm a suspicion. He took a look at the leaves of one of the trees and saw the spots and yellow leaf veins.

There was no doubt: Huanglongbing had spread to the United States.

Also known as citrus greening disease, huanglongbing is a bacterial plant disease wherein the bacteria disrupt the nutrient transport system, essentially starving the plant. Leaves change color first and then the tree produces stunted, bitter-tasting fruit. After a few years, many infected trees die. "And we knew from other countries how fast the disease spreads," Irey says.

Just a few days after the initial discovery, USDA staff found two additional cases, this time in orange plantations. Soon, the disease had spread across Florida. Orange production in the state has plunged by around 70 percent since 2005. If the disease continues to spread, Florida may soon grow no oranges at all.

Orange producers, not surprisingly, went on war footing -- including Southern Gardens Citrus, Irey's current employer. The company is an industry heavyweight, producing orange juice for brands like Tropicana and Minute Maid. Workers felled the infected trees and began spraying twice as often as they used to. They also gave the trees additional nutrients and conducted tests with antibiotics. But nothing really helped.

Then, Michael Irey heard about designer viruses for the first time.

The creation of custom-designed biological assistants is among the greatest promises of synthetic biology. Scientists dream of one day being able to construct viruses or bacteria from a collection of building blocks. Like a molecular delivery service, the viruses would deliver their genetic material to the cells of plants, animals or even people, where they would then fulfill their mission: boosting the production of certain proteins or directly manipulating the cell's genetic makeup.

The technology's potential promise for agriculture is enormous. Plant viruses that pose no danger to humans could protect olive orchards and orange plantations from disease or shield staples like corn and rice from the effects of drought or strong rains. And they could be deployed rapidly. Viruses could help farmers prepare their plants for possible threats as early as the germination phase -- and humans could get the upper hand on nature faster than ever before.

Unwanted Enemies

In Florida, Southern Gardens Citrus began working on the super-viruses together with other scientists. In Europe, an association of 17 research institutions and companies receive more that 3 million euros from the EU to study the potential of such viruses for the agricultural industry. And some scientists in the U.S. have even taken a step further: They are breeding aphids and leafhoppers that will have the ability to transmit the viruses to plants. The program, which receives financing from the U.S. government's Defense Advanced Research Projects Agency (DARPA), is called Insect Allies.

But those allies, it is feared, could turn into unwanted enemies.

Experts are concerned that the gen-tech viruses could be transmitted to other plant species and begin spreading uncontrollably. Some scientists have also issued a warning aimed specifically at the DARPA program that the technology could fall into the wrong hands and be transformed into a dangerous biological weapon. Indeed, the line between high-tech helper and horrific threat appears to be a fine one.

On the shoulder of a four-lane highway in southern Florida, Michael Irey unlocks a gate with a sign: "Notice! This gate must be kept locked!" Irey drives his pickup down a dusty dirt track, which comes to an end after a couple of kilometers at an orchard with 12 rows of orange trees. Irey says the location of the orchard is secret "for reasons of security."

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