Trees genetically modified to resist citrus greening are grown in a greenhouse in South Florida.
Trees genetically modified to resist citrus greening are grown in a greenhouse in South Florida.

Slow progress in Florida is being made that some feel may be the most effective means of combating the dreaded citrus greening disease–genetically modified organisms, or GMOs.

Like thousands of Florida growers, Southern Gardens Citrus in Clewiston, which once had 2.5 million citrus trees that primarily produce juice oranges, chopped down hundreds of thousands of trees—about 25 percent of its plantings. It also sprayed a variety of pesticides in an attempt to slow the disease, all to no avail.

Then, when a worldwide search failed to find a tree that was immune to the disease or the Asian citrus psyllid that spreads it, president Rick Kress decided transgenics/GMOs may be the answer.

“We’ve got to develop a solution that solves the disease and protects the industry and is proven safe for the consumer,” Kress says. “If the researchers of the world are accurate, they’ve indicated that the ultimate solution to this disease is going to involve genetics.”

Southern Gardens embarked on a program in 2007 to develop a transgenic tree that may end up costing $20 million. The company may be able to recoup some of its investment, though, by selling transgenic trees to other growers.

Hopeful for a solution

“I believe we’re going to find a solution,” Kress says. But he admits that solution still could be five or six years away—or more.

As a first step, Kress and Southern Gardens research director Michael Irey selected five scientists to underwrite. From those five, they chose the researchers they felt would do the best job of finding a gene that would attack the bacteria or the psyllid

Two of the researchers they considered used a gene from vegetables, one used a gene from a virus and another used one from a pig. The last scientist proposed a synthetic gene.

“We fully expect that we will be able to ultimately combine research work from more than one of our researchers,” Kress says. But for now, he chose to focus on the work of Erik Mirkov of Texas A&M University, who already was working with trees into which he had spliced a spinach gene.

Mirkov says his gene-splicing technique could be applicable to citrus varieties in all growing areas, including California, Texas and Arizona, as well as Florida and, eventually, perhaps even outside the United States.

Kress quickly allayed the fears of growers by assuring them that their oranges will not take a green hue or taste like spinach.

Mirkov says his program must go through an extensive approval process, which will include three federal agencies—the U.S. Department of Agriculture, the Environmental Protection Agency and the Food and Drug Administration.

“As our research progresses, the regulatory approval process is in place and moving forward,” Kress says, adding that approval could take two to four years.

Other research financed by growers and the U.S. Department of Agriculture also is being conducted, including developing a genetically modified orange. And Kress says he’ll be pleased to find any solution.

New front

Even if the program does produce a tree that is immune to citrus greening, the battle may switch to another front.

Polls indicate that up to one-half of U.S. consumers say they will not eat transgenic food despite studies by the government and other researchers that say it poses no threat to humans or the environment.

“If it works, there’s got to be consumer education and consumer understanding, and there’s got to be the necessary work done to show that it’s safe,” Kress says. “That’s all part of the process.”

The industry will have a better understanding of how the public might react to the concept of GMOs and citrus after the Public Issues Education Center at the University of Florida’s Institute of Food and Agricultural Sciences at Gainesville releases the results of a public opinion survey in November.

That survey is designed to determine the public’s perception of GMOs as they relate to citrus and citrus greening disease, says Tracy Irani, the center’s director.

Before genetically altered citrus is marketed, she says, “We’ll need to do a good job of measuring what the public’s perception is about GMOs because it changes over time.”

“We don’t really know what the general viewpoint is of the public,” she says.

There likely are a range of opinions.

The fact that GMOs and citrus may have a direct benefit to consumers in terms of lower prices and increased availability may raise more interest than other programs that result in indirect benefits, such as herbicide tolerance or pest resistance, she says.

“The greening aspect provides an opportunity for scientists to talk about what they know,” she adds.

Growers likely will be willing to plant genetically modified trees if they’re shown to be effective against citrus greening as long as consumers accept them, says Andrew Meadows, director of communications for Lakeland-based Florida Citrus Mutual.

“Growers will accept anything that’s accepted by the marketplace,” he says. “The acceptance starts and ends with the consumer.”

No quick solution

If the industry decides to move forward with transgenic trees, change won’t happen overnight.

“Today in Florida, there are approximately 60 million trees that may have to be replaced,” Kress says. “This will take time.”

He expects the first trees to be planted in the next two to four years.

“Full involvement by the industry will be dependent upon the available capacities of nursery operations to grow the trees,” Kress says.

He says it’s not possible today to estimate what the cost of a disease-resistant tree will be for growers, since it’s not known what the total cost of development will be. But he acknowledged that, “if the cost of a disease-resistant tree is prohibitive to the grower, replanting may not be a good business decision.”

Other research

William Dawson, a plant pathologist at the UF Citrus Research and Education Center in Lake Alfred, also is looking into GMOs and citrus.

“We have those constructs, and we’re looking at it independently,” he says. “We don’t have an answer yet.”

Dawson says he and other researchers also have produced transgenic plants.

“We’re screening about 100 different things,” he says. “We’re hoping we can find something in the 100, but we’re still looking and trying and scraping and digging and beating our head against a wall.”

Getting a definitive test is time consuming, he says, and researchers are getting many variations in their controls.

Meadows emphasizes that GMOs are only one tool the industry is looking at to fight citrus greening. The industry has been using coordinated pesticide management efforts, and there is research into biological controls, for example.

“We’re hopeful,” Dawson says. “We’re running just as fast as we can.”