Has a Cure Been Found for Citrus Greening?

inspecting a citrus leaf for HLB symptoms

A citrus greening cure has been a dream for many in the industry impacted by the disease. Is a new discovery involving Australian finger lines the dream come true? Photo by Frank Giles

University of California, Riverside (UCR) scientists say they have found the first substance capable of controlling citrus greening, a disease that has devastated farms in Florida for well more than a decade and now also threatens the industry in California.

According to researchers, the new treatment effectively kills the bacterium causing the disease with a naturally occurring molecule found in wild citrus relatives. The molecule, an antimicrobial peptide, offers numerous advantages over the antibiotics currently used to treat the disease.

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UCR Geneticist Hailing Jin, who discovered the treatment after a five-year search, explained that unlike antibiotic sprays, the peptide is stable even when used outdoors in high heat, easy to manufacture, and safe for humans.

“This peptide is found in the fruit of Australian finger limes, which can naturally tolerate citrus greening bacteria and has been consumed for hundreds of years,” Jin said. “It is much safer to use this natural plant product on agricultural crops than other synthetic chemicals.”

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Currently, some growers in Florida are spraying antibiotics and pesticides in an attempt to save trees from the CLas bacterium that causes citrus greening — aka, HLB.

“Most antibiotics are temperature sensitive, so their effects are largely reduced when applied in the hot weather,” Jin said. “By contrast, this peptide is stable even when used in 130°F heat.”

Jin found the peptide by examining plants known to possess natural tolerance for the bacteria that causes citrus greening, and she isolated the genes that contribute to this innate immunity. One of these genes produces the peptide, which she then tested over the course of two years.

“You can see the bacteria drastically reduced, and the leaves appear healthy again only a few months after treatment,” Jin said.

Because the peptide only needs to be reapplied a few times per year, it is highly cost effective for growers, Jin points out. It also can be developed into a vaccine-like spray to protect young healthy plants from infection, as it is able to induce the plant’s innate immunity to the bacteria. It moves systemically through plants and remains stable.

Plans are to further enhance the treatment with proprietary injection technology made by Invaio Sciences. UC Riverside has entered into an exclusive, worldwide license agreement with the plant tech company to ensure this new treatment is delivered efficiently.

“The prospect of addressing this previously incurable and devastating crop disease, helping agricultural communities, and improving the environmental impact of production is exciting and rewarding,” Invaio Chief Science Officer Gerardo Ramos said. “This is crop protection in harmony with nature.”

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