citrus greening

Dr. Evan Johnson, a specialist in plant pathology, explains the signs and symptoms of citrus greening at the University of Florida’s Citrus Research and Education Center in Lake Alfred. Photos courtesy UF/IFAS


Nutrient supplements, root-stock additives, genetic modification, heat therapies and a bacterial killer are just a few of the proposed solutions to what has been called the worst disease in history to hit Florida orange groves: citrus greening. This bacterial disease prevents nutrients from being absorbed by the infected tree, is killing off Florida orange trees and, with them, the state’s orange juice industry, which supplies 80 percent of the U.S. market.

Oranges with citrus greening

Oranges with citrus greening. The disease has devastated the state’s citrus industry.

Fighting Citrus Greening

Many researchers are working to find a cure, like Dr. Reza Ehsani, a University of Florida Institute of Food and Agricultural Sciences scientist who is using unmanned aerial vehicles — drones — to diagnose areas of citrus greening in groves. One of the newest solutions from the University of Florida suggests the protein that spreads citrus greening in a tree can be killed with a biochemical spray. All proposed solutions require years-long field testing and approval before any cure is brought to the grower on the grove.

Money helping to fight the disease

While the industry that defines Florida makes its way toward a recovery, thanks to millions of dollars in new research money, delivering a cure to the grower takes time, at a time when growers continue to absorb production losses.

Associate Professor of Microbiology and Cell Science Nian Wang, also of UF/IFAS, studies two major citrus diseases: citrus canker and citrus greening, also known as huanglongbing (HLB). Wang works to control these diseases by finding information about the mechanisms that cause them.

Wang said, “The citrus industry is facing challenges from both HLB and canker, especially HLB. I hope our work will lead to a long-term and sustainable solution to control HLB and canker by generating HLB and canker-resistant citrus varieties.”

Gene editing seems effective

One method that Dr. Wang’s lab has used is gene editing, in which researchers use a technique called CRISPR (clustered regularly interspaced short palindromic repeats) — a new genome editing tool — to modify the DNA in grapefruit, thus creating a new variety resistant to citrus canker. His lab was the first to adopt CRISPR technology to conduct genome editing of citrus.

Dr. Wang explained, “This technology can generate HLB-resistant and -tolerant genome-edited citrus varieties that are free of foreign DNA, and thus can be commercialized immediately.”

Following this success, Wang was awarded $1 million from the Florida Legislature to use the CRISPR system to develop varieties of citrus that are resistant to citrus greening.

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