Spinach Peptide Discovery Leads To Citrus Greening Treatment

A new treatment for citrus greening disease, built on more than a decade of research involving Texas A&M AgriLife scientists, has reached a major milestone on its way to commercial use.

The U.S. Environmental Protection Agency has granted unconditional registration to a new therapy designed to help citrus trees fight Huanglongbing, commonly known as citrus greening. The disease is considered one of the most destructive threats facing citrus production in the United States.

The product is registered by Maryland-based Silvec Biologics Inc. and is based on research pioneered at the Texas A&M AgriLife Research and Extension Center at Weslaco.

Kranthi Mandadi, Ph.D., center director and professor in the Texas A&M Department of Plant Pathology and Microbiology, worked with researchers at the University of Florida to develop the technology. The research ultimately demonstrated that naturally occurring antimicrobial peptides found in spinach, known as defensins, could help protect citrus trees from the bacteria associated with citrus greening.

How the Treatment Works

The treatment combines the spinach-derived defensins with a specially developed strain of citrus tristeza virus, or CTV, that acts as a delivery system inside the tree.

Researchers use a naturally non-transmissible strain of CTV already found in Florida citrus trees and modify it so that it prompts the tree to produce the spinach-derived defensin peptide.

A small piece of plant material from a specially developed source tree is grafted onto an existing citrus tree. The benign CTV then becomes established within the tree and continually produces the defensin peptide, helping the tree fight the bacteria associated with citrus greening.

The process does not alter the citrus tree’s genome. Instead, researchers have compared the approach to an immunization that gives the tree an ongoing defense against the disease.

Years of Research Lead to EPA Registration

The EPA registration was issued under the Federal Insecticide, Fungicide and Rodenticide Act and allows the spinach defensin-based therapy to be sold commercially without a tolerance limit.

The registration follows years of research, safety testing, peptide screening and field trials involving public universities, agricultural organizations and private companies.

Mandadi’s work grew from earlier research with AgriLife Research professor and plant pathologist Erik Mirkov, Ph.D. The researchers identified spinach defensin peptides as a potential tool for protecting citrus trees from greening disease.

Early studies supported by AgriLife Research, the Foundation for Food and Agricultural Research and Southern Gardens Citrus helped move the technology from laboratory research into advanced testing and field trials.

Public and Private Partners Move Treatment Toward Market

The research eventually resulted in patents covering different parts of the technology. The Texas A&M University System patented the defensin technology, while the University of Florida patented the CTV delivery system.

Patent rights to both technologies were licensed to Southern Gardens Citrus, a subsidiary of U.S. Sugar, which supported continued research and development. The rights were later sublicensed to Silvec Biologics to pursue EPA registration, commercialization and distribution.

The overall research and development effort stretched across approximately 15 years and involved multiple public and private institutions.

Funding and support came from programs including the U.S. Department of Agriculture’s National Institute of Food and Agriculture Emergency Citrus Disease Research and Extension Program, the AgriLife Research Insect Vectored Diseases program and Texas A&M University’s Advancing Discovery to Market funding program.

New Option for Citrus Growers

Citrus greening has devastated citrus-producing regions by weakening infected trees, reducing fruit quality and production and eventually causing trees to decline. There is currently no simple cure for an infected tree, making treatments that can keep trees healthy and productive especially important to growers.

The newly registered therapy is intended to provide growers with another way to maintain citrus production despite disease pressure.

According to Silvec, growers are expected to begin gaining access to the product in Florida in late 2026 through the state’s Citrus Research and Field Trial, or CRAFT, program.

Researchers are also exploring whether spinach defensins could be used against other agricultural diseases. Current work includes potential applications for potatoes affected by zebra chip disease as well as new peptide combinations and delivery systems that could eventually provide protection for additional crops.

The EPA registration marks an important step in moving the technology from years of laboratory and field research into a product that can be used by commercial citrus growers.