Promising technology arises in fight against potentially devastating citrus disease

By John Cox | |

BAKERSFIELD.COM - Researchers in Riverside and Maryland may have come up with a breakthrough in the fight against a pest-borne bacterial disease threatening to wipe out California's citrus industry.

A kind of virus first spotted in the 1950s, when the leaves on four limequat trees in Indio developed yellow veins, has been found to spread effectively throughout citrus trees' vascular systems. Although not itself medicinal, the material could prove useful to delivering helpful therapies.

While a patent is still pending and a considerable about of testing remains to be done, hopes are high enough that a company founded to commercialize the discovery reports having already raised millions of dollars from investors.

Work done by two researchers at the University of California, Riverside — citrus pathology specialist Georgios Vidalakis and UCR plant virologist Kiran Gadhave — as well as University of Maryland scientist Anne Simon has won financial support from the California Citrus Research Board in Visalia.

The board's chief research scientist, Melinda Klein, said the research appears promising because it may open the way for therapies that are otherwise hard to disseminate throughout citrus trees.

If tests prove the approach is safe, not only could it allow farmers to treat their orchards for diseases, but it could also help them fight insects carrying them.

What's more, it appears the newly identified material could act as a vessel for carrying a certain protein preliminarily believed to offer the potential for inoculating mandarin, orange and lemon trees against the so-far incurable disease known as Huanglongbing. The promising protein, announced publicly about a year ago, also came out of UCR laboratories.

"These are complementary technologies," Klein said. "They could be of great benefit to both California growers and growers across the United States."

Huanglongbing has been identified in Southern California after it decimated Florida's citrus industry. Although it has not been reported in the Central Valley, the insect that carries it — the tiny, winged Asian citrus psyllid — has been found throughout the valley portion of Kern and agricultural areas further north.

Vidalakis said he came across the viral molecule associated with yellow vein disease while going over diseased trees first found in the 1950s. The pathogen causing veins to yellow did not appear to harm the trees but it did seem to have unique properties.

He said he didn't realize the molecule's medicinal potential until Simon contacted him about five years ago to say the molecule could potentially treat diseases. He said when he protested that its efficiency doesn't seem to make sense, "she said, 'No, no, it's perfect.'"

The molecule replicates efficiently and does not appear to spread to other organisms, he said. It's also small enough to be easily manipulated in a laboratory, he said, making it ideal for pairing with different therapies.

"You have a very nice set of properties that make this system very, very promising to deliver all sorts of therapies in the vascular tissue of citrus," he said.

If tests show the molecule is safe for plants and the environment, a process that could take between three and 10 years, then the plan would be to grow one or more "mother" trees whose material could be grafted onto trees growing in citrus orchards. That means the therapies would not have to be put into chemicals for spraying as pesticides.

Still to be determined, he said, is whether the molecule silences citrus genes or harms useful bacteria living in trees.

Gadhave, the project's lead researcher, said the molecule appears to offer great potential even for non-citrus plants.

"We are trying to see if this is going to work in the field, and this is where I come in, actually," he said.

Simon's entrepreneurial brother, Rafael Simon, said UCR and the University of Maryland together filed for a patent in 2019. While the application is still being processed, he expects a proof of concept will emerge next year.

Meanwhile, he has founded a Maryland-based company called Silvec Biologics that aims to commercialize the technology. He said it has received grant money from the U.S. Department of Agriculture, plus millions of dollars in venture capital.

His expectation is that the molecule will work in grapes, apples and other fruit, not just citrus, and that it will be used to fight diseases beyond just Huanglongbing.

"We're hoping to vaccinate against everything," he said


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