Mike Roberts

Antimicrobial Peptide Can Combat Citrus Greening

Florida citrus growers have been waiting a long time for a method to combat citrus greening, and they just may have it in the antimicrobial peptide discovered by UC Riverside geneticist Hailing Jin and her team. Jin discussed the ongoing research into the peptide at the 2021 Florida Citrus Show, and she maintained that the research so far has shown that the peptide can both inhibit Candidatus Liberibacter asiaticus (CLas) growth in trees already infected with citrus greening and activate immunity in noninfected citrus trees to keep them from becoming infected. The antimicrobial peptide has many other benefits as well.

Benefits of the Antimicrobial Peptide

The peptide was discovered in citrus finger limes, a wild Australian citrus relative that is tolerant to citrus greening. The peptide has many advantages in addition to combating citrus greening both in infected trees and noninfected trees, an uncommon attribute of such treatments. According to Jin, the peptide features a “corkscrew-like helix structure” that punctures the bacteria that cause citrus greening—Candidatus Liberibacter asiaticus (CLas)—and cause the bacteria to die much faster than any antibiotics currently in use.

The research also showed that the peptide could be applied using an injection or through a spray application, that it was stable up to 130-degree heat, and that it was safer than synthetic treatments because it comes from a natural source. In testing the peptide’s efficacy in a spray application, researchers introduced citrus greening to 10 noninfected citrus trees via Asian citrus psyllids that were positive for the CLas bacterium. After several interval sprays with the peptide, only three of the trees tested positive for citrus greening. In the test group, nine citrus trees tested positive for citrus greening, and four of the trees died.

Field testing of the antimicrobial peptide is currently underway in Florida, and hopefully it’s only a matter of time until it becomes a treatment that Florida citrus growers can utilize in the fight against citrus greening.

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