Citrus Greening Prevention – Focus of $1.2Bln Research Project

Dr. Kranthi Mandadi, assistant professor in the department of plant pathology and microbiology at the Texas A&M AgriLife Research and Extension Center-Weslaco. Photo: Texas A&M AgriLife

Citrus greening, also known as Huanglongbing disease, has devastated citrus fruit crops in Florida, Texas and California. USDA has funded citrus greening prevention research with a $1.2 billion grant.

The project involving researchers in major citrus fruit producing regions will be led by Kranthi Mandadi, assistant professor in the  Texas A&M AgriLife  plant pathology and microbiology department.

“We are implementing an innovative pilot-scale antimicrobial screening and discovery pipeline to help find therapies to control citrus greening,” said Mandadi.

“This collaborative research is addressing a major economic issue affecting citrus growers in Florida, Texas and California,” said Bill McCutchen, executive associate director of AgriLife Research in College Station. “We are hopeful that new high throughput screening process will lead to multiple discoveries to mitigate the threat of citrus greening and other hard to detect pathogens and diseases while enhancing quality and yields.”

 “With citrus greening disease, and with many other related plant diseases, a major challenge is the pathogens that cause them are unculturable,” Mandadi said. “This stymied our ability to test new therapies that are effective against these pathogens. A key aspect of our project is that we are utilizing an innovative approach to cultivate these pathogens in so called ‘hairy roots’ which enables faster bioassays in the lab.”

Citrus greening on tree leaf. Photo: University of Florida Extension

Currently, several antimicrobials are being utilized or tested against citrus greening including antibiotics, defense modulators and zinkicides. 

To evaluate their efficacy, the conventional approach is to perform foliar or leaf sprays, injections, soil drenching or to screen against other distant surrogate pathogens that can be cultured. 

The screening and effectiveness with traditional research methods can be inconsistent and costly when trying to work with mature trees, thus limiting the ability of researchers to screen the vast number of chemistries that exist. 

Using the hairy root-based bioassays, the screening of antimicrobials (small molecules and peptides) against the pathogens can be performed in vitro much faster, thus saving significant amounts of resources and time, which the citrus industry is running short on.

“The idea is to couple the hairy root screening platform with the latest genomic and computational modeling tools to discover antimicrobials directly blocking citrus greening pathogen proteins and deliver them in a much shorter time-frame,” McCutchen said. “Such target-based screening approach, common in biomedical drug discovery, hasn’t been employed much for tackling plant disease. Once shortlisted, potent antimicrobials will be considered for greenhouse and field tree evaluations.”

The joint collaboration includes researchers from Texas A&M; University of California Lindcover Research and Extension Center; University of Florida Citrus Center;  University of Florida Citrus Center and Southern Gardens Citrus.

The research grant of approximately $1.2 million was awarded by the U.S. Department of Agriculture-National Institute of Food and Agriculture, Emergency Citrus Disease Research and Extension.


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