Australian finger limes have a natural resistance to citrus greening, or HLB. Previous work by scientists at the University of California Riverside (UCR) led to the discovery of a peptide in these finger limes that will effectively kill the citrus greening bacterium when introduced to other trees as a treatment option. The UCR research team also collaborates with USDA and universities in Texas, Florida, and Washington. Their work collectively is bringing the big citrus growing communities together in their research to solve every citrus grower’s biggest disease problem. Once the innate immunity to HLB was discovered in the Australian finger lime, UCR researchers isolated the genes contributing to this natural defense. One gene produces a crucial peptide that works in this HLB defense.
Today, common antimicrobial sprays used to hold the citrus greening infection back can be costly and need to be applied often. This peptide was applied similarly in early-stage trials in the laboratory and greenhouse, which demonstrated great results in overcoming the pathogen systemically in young citrus trees. Applying this natural peptide by foliar spray and injection
both allow for systemic uptake and movement throughout the trees. The early trial results showed significant improvement in the health of the young citrus trees and an extreme reduction in HLB bacteria present in the trees, after just a few months of treatment with this peptide.
The citrus-derived peptides effectively prevented HLB infection in young citrus trees and was also active in treating young HLB-infected trees. Furthermore, it is stable and not as sensitive to high heat as antimicrobials, making the treatment stronger and more effective in comparison to other current applications. Now the team is working on breeding new citrus using their genetic knowledge of this natural resistance to HLB. They hope to provide a more sustainable solution to this deadly disease by incorporating the resistance into the trees’ DNA through breeding methods.
UCR researchers will be generating a lot of resistant hybrids in this project, many of which won’t have the ideal fruit traits needed for marketable produce. Australian finger limes have a sharp, bitter taste compared to marketable citrus fruits like oranges. Extensive trials and selections will be done to find the best mix of HLB resistance and sweet marketable fruit. Many challenges are sure to arise during the breeding process and trialing for the best marketable varieties will take time. Planting naturally HLB-resistant trees will provide a better economical and sustainable look to the citrus industry’s future overall.