BEIJING - Scientists have uncovered the first known natural defense mechanism against citrus greening disease, a deadly plant illness that has devastated citrus farms worldwide.

The breakthrough, led by a research team from the Institute of Microbiology of the Chinese Academy of Sciences (IMCAS), was published in the journal Science.

Citrus greening disease, also called huanglongbing (HLB), is often referred to as the "cancer of citrus" because it slowly kills trees and has no known cure. Spread by tiny insects, the disease has ruined millions of acres of citrus crops across 50 countries, costing farmers billions of dollars each year. Once a tree is infected, it usually dies within a few years.

The research team discovered that some citrus-related plants, like the curry leaf plant and Sichuan pepper plant, naturally resist the disease. They found that these plants produce a special protein that helps them fight off the HLB bacteria. By studying this protein, scientists were able to modify citrus trees to make them more resistant.

The team also used artificial intelligence to design small protein fragments, called peptides, that can block the disease. In tests, one of these peptides, named APP3-14, reduced infection rates by up to 80 percent in a single season.

"This discovery gives us two powerful tools," said Ye Jian, a professor at the IMCAS. "First, we can develop eco-friendly treatments to protect trees. Second, this method could help fight other plant diseases that are hard to control."

The findings bring new hope to citrus farmers struggling with HLB and may lead to similar solutions for other crop diseases, such as maize rust fungus and olive tree infections, he added.