California Researchers Seek HLB Tolerance

Tacy CalliesCalifornia Corner, HLB Management, Research

Asian citrus psyllid nymphs transmit the bacterium that causes HLB disease.

University of California, Riverside (UCR) has received three federal grants totaling more than $11 million for research focused on instilling HLB-tolerance in citrus trees. The grants are from the U.S. Department of Agriculture’s (USDA) National Institute of Food and Agriculture (NIFA). The funding was enabled by the 2018 Agricultural Improvement Act, which authorized the Emergency Citrus Disease Research and Development Trust Fund to fight HLB.

The largest of the UCR projects, at $6.8 million, is led by Danelle Seymour, assistant professor of genetics in the UCR Botany and Plant Sciences Department. The focus is on breeding HLB-resistant rootstocks. The project depends on collaboration with Kim Bowman, a citrus breeder at the USDA Agricultural Research Service in Fort Pierce, Florida.

“In citrus, it takes 10 to 15 years to evaluate a new generation of trees,” Seymour said.

Because of the long lag time, the research-ready trees in Florida represent an opportunity for Seymour’s team to begin examining new crosses now. Bowman has evaluated more than 10,000 trees and unique hybrids, from which a handful will be selected for release to growers.

The researchers also will be watching the Florida-grown trees’ responses to the different environmental conditions in California.

Chandrika Ramadugu, a project scientist in UCR’s Botany and Plant Sciences Department, is leading a project to develop HLB-resistant scion varieties that can be grafted to rootstocks. With a grant of $3.28 million, this project will analyze second-generation hybrids that are bred for 10 years using Australian lime as a source of disease resistance. 

Ramadugu will evaluate 24 novel hybrids in California, Florida and Texas to assess resistance to HLB. Ideally, the new plants will also be able to produce good-tasting fruit. The new hybrids may also help protect citrus from other pests and pathogens. 

A third project, granted $1.36 million, will utilize a peptide found in Australian finger limes that is known to impart HLB resistance. Led by Hailing Jin, microbiology and plant pathology professor, the project is developing ways to infuse trees with the peptide. 

“The antimicrobial peptide in the finger limes is more efficient at killing bacteria as compared to antibiotics currently used in the field, and much more stable at high temperatures,” Jin said. 

In collaboration with University of Florida professor Svetlana Folimonova, Jin’s team utilizes a natural citrus virus with almost no symptoms to deliver the peptide into the trees. 

“You infect the tree with the virus, and it will spread in areas where the bacteria reside,” Jin said. “It would move systemically through the tree, and it would be very cost efficient for growers.”

Source: UCR