Experts race to save oranges from disease by altering DNA

Published: Sunday, Jul. 28, 2013 - 12:00 am | Page 15A
Last Modified: Monday, Jul. 29, 2013 - 8:21 am

CLEWISTON, Fla. – The call Ricke Kress and every other citrus grower in Florida dreaded came while he was driving.

"It's here" was all his grove manager needed to say to force him over to the side of the road.

The disease that sours oranges and leaves them half green, already ravaging citrus crops across the world, had reached the state's storied groves. Kress, the president of Southern Gardens Citrus, in charge of 2.5 million orange trees and a factory that squeezes juice for Tropicana and Florida's Natural, sat in silence for several long moments.

"OK," he said finally on that fall day in 2005, "let's make a plan."

In the years that followed, he and the 8,000 other Florida growers who supply most of the nation's orange juice poured everything they had into fighting the disease they call citrus greening.

To slow the spread of the bacterium that causes the scourge, they chopped down hundreds of thousands of infected trees and sprayed an expanding array of pesticides on the winged insect that carries it. But the contagion could not be contained. They scoured central Florida's half-million acres of groves and sent search parties around the world to find a naturally immune tree. But such a tree did not exist.

"In all of cultivated citrus, there is no evidence of immunity," the plant pathologist heading a National Research Council task force on the disease said.

With a precipitous decline in Florida's harvest predicted within the decade, the only chance left to save it, Kress believed, was one his industry and others had long avoided for fear of consumer rejection. They would have to alter the orange's DNA – with a gene from a different species.

Oranges are not the only crop that might benefit from genetically engineered resistance to diseases for which standard treatments have proved elusive. Advocates of the technology say it could help provide food on a warming planet. Leading scientific organizations have concluded that shuttling DNA between species carries no intrinsic risk to human health or the environment.

But the idea of eating plants and animals whose DNA has been manipulated in a laboratory – called genetically modified organisms, or GMOs – still spooks many people. Critics worry that such crops carry risks not yet detected and distrust the agrochemical companies that have produced the few in wide use. Kress' boss worried about damaging the image of juice promoted as "100 percent natural."

Kress, now 61, had no particular predilection for biotechnology. But an emerging scientific consensus held that genetic engineering would be required to defeat citrus greening.

"People are either going to drink transgenic orange juice or they're going to drink apple juice," one University of Florida scientist told Kress.

If the presence of a new gene in citrus trees prevented juice from becoming scarcer and more expensive, Kress believed, the American public would embrace it.

Plunging ahead

Early discussions among other citrus growers about what kind of disease research they should collectively support did little to reassure Kress about his own genetic engineering project.

"The public will never drink GMO orange juice," one grower said at a contentious 2008 meeting. "It's a waste of our money."

If various polls were to be believed, a third to half of Americans would refuse to eat any transgenic crop.

"The public is going to be more informed about GMOs by the time we're ready," Kress told his research director, Michael Irey, as they lined up the five scientists whom Southern Gardens would underwrite.

It would cost Southern Gardens millions of dollars just to perform the safety tests for a single gene in a single variety of orange. Of his five researchers' approaches, Kress had planned to narrow the field to the one that worked best over time.

But in 2010, with the disease spreading faster than anyone anticipated, the factor that came to weigh most was which could be ready first. One contender, Erik Mirkov of Texas A&M University, had endowed trees with a gene from spinach – a food, he noted, "we give to babies."

The gene, which exists in slightly different forms in hundreds of plants and animals, produces a protein that attacks invading bacteria.

In fall 2010, Mirkov's trees were put to the test inside a padlocked greenhouse stocked with infected trees and psyllids. In a greenhouse where every nontransgenic tree had showed symptoms of disease, the trees with the spinach gene survived unscathed for more than a year. Kress would soon have 300 of them planted in a field trial.

In spring 2012, he asked the Environmental Protection Agency, the first of three federal agencies that would evaluate his trees, for guidance. The next step was safety testing.

A growing urgency

Other concerns weighed on Kress that spring: Growers in Florida did not like to talk about it, but the industry's tripling of pesticide applications to kill the bacteria-carrying psyllid was, while within legal limits, expensive and worrisome. And a vocal movement to require any food with genetically engineered ingredients to carry a "GMO" label had made him uneasy.

When the EPA informed him in June 2012 that it would need to see test results for how large quantities of spinach protein affected honeybees and mice, Kress gladly wrote out the $300,000 check to have the protein made. If these tests raised no red flags, he would need to test the protein as it appears in the pollen of transgenic orange blossoms.

Rather than wait for Mirkov's 300 trees to flower, which could take several years, they agreed to try to graft his spinach gene shoots to mature trees to hasten the production of pollen – and, finally, their first fruit, for testing.

Driving in October to speak at the California Citrus Growers meeting, Kress considered how to answer critics. Maybe even a blanket "GMO" label would be OK, he thought, if it would help consumers understand he had nothing to hide. He could never prove there were no risks to genetically modifying a crop. But he could try to explain the risks of not doing so.

Southern Gardens had lost 700,000 trees trying to control the disease, more than a quarter of its total. The harvest forecast was dismal.

What growers wanted most, he knew, was reassurance that he could help them should the disease spread. But he had to warn them: "If we don't have consumer confidence, it doesn't matter what we come up with."

Healthy trees

One recent sunny morning, Kress drove to a fenced field far from any other citrus tree. He unlocked the gate and signed in.

Just in the previous few months, Whole Foods had said that because of customer demand it would avoid stocking most GMO foods and require labels on them by 2018. The Agriculture Department had issued its final report for this year's orange harvest showing a 9 percent decline from last year, attributable to citrus greening.

But visiting the field gave Kress some peace. In some rows were the trees with no new gene in them, sick with greening. In others were the 300 juvenile trees with spinach genes, all healthy. In the middle were the trees that carried his immediate hopes: 15 mature trees, 7 feet tall, onto which had been grafted shoots of Mirkov's spinach gene trees.

There was good reason to believe the trees would pass the EPA's tests when they bloom next spring. He was gathering the data the Agriculture Department would need to ensure that the trees posed no risk to other plants. When he had fruit, the Food and Drug Administration would compare its safety and nutritional content to conventional oranges.

Late this summer Kress will plant several hundred more young trees with the spinach gene, in a new greenhouse. In two years, if he wins regulatory approval, they will be ready to go into the ground.

The trees could be the first to produce juice for sale in five years or so.

© Copyright The Sacramento Bee. All rights reserved.

Read more articles by Amy Harmon





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