Genetically modified HLB-resistant citrus trees move to field trials

05/11/2011 04:08:00 PM
By Tom Burfield

The most effective method of controlling the devastating citrus greening disease that has ravaged Florida’s orange groves also may be the most controversial.

A report from the National Academy of Sciences says the most powerful long-time management tool for the bacterium that causes the disease and, possibly, for the Asian citrus psyllid that spreads it, may be genetic engineering.

“Genetic engineering, in the form of transgenic citrus or citrus inoculated with a transgene-expressing virus vector, holds the greatest hope for generating citrus cultivars resistant to (the causal bacterium and the psyllid),” the report says.

At the same time, the report warns that groups opposed to genetically modified foods of any kind may try to dissuade the public from turning to genetically engineered orange juice.

Work goes on

Meantime, efforts continue toward finding a solution to citrus greening, also called huanglongbing—or HLB—which now is present in nearly all of Florida’s citrusproducing counties but is most prevalent in the southern areas of the state.

The state’s citrus industry is well worth preserving.

“There would be great repercussions for Florida’s economy if the estimated $9.3 billion annual economic benefit of the citrus industry were to be lost or significantly diminished,” the NAS report says.

T. Erik Mirkov, professor of plant virology at Texas A&M University in College Station, has been at the forefront of the search for a genetic solution to greening disease and appears to be making progress.

“We’ve found some genes in spinach that we’ve transferred into citrus that provide resistance,” he says.

Mirkov has received a permit from the U.S. Department of Agriculture to conduct field testing of trees in Florida.

“We’ve got good results in the greenhouse, and now we’re making sure it holds up in the field,” he says.

Although Mirkov’s work appears promising, he still has a way to go. “We don’t have what I would call immunity quite yet,” he says.

Nationwide threat

Although the disease so far has wreaked havoc in Florida, it also poses a threat to citrus industries in Texas, California and other states.

“It’s the citrus grower’s worst nightmare,” Mirkov says.

One of the most challenging aspects of the disease is that a tree can be a source of infection even before it shows any symptoms.


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