A perspective on current therapeutic molecule screening methods against ‘candidatus liberibacter asiaticus’, the presumed causative agent of citrus Huanglongbing

Authors: Kennedy, John; WOOD, KIMBERLY - Agrosource, Inc; PITINO, MARCO - Agrosource, Inc; MANDADI, KRANTHI - Texas A&M University; IGWE, DAVID - Cornell University; Shatters, Robert - Bob; Widmer, Timothy; Niedz, Randall; Heck, Michelle

Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/3/2023
Publication Date: 2/7/2023
Citation: Kennedy, J.P., Wood, K., Pitino, M., Mandadi, K., Igwe, D., Shatters, R.G., Widmer, T.L., Niedz, R.P., Heck, M.L. 2023. A perspective on current therapeutic molecule screening methods against ‘candidatus liberibacter asiaticus’, the presumed causative agent of citrus Huanglongbing. Phytopathology. https://doi.org/10.1094/PHYTO-12-22-0455-PER.
DOI: https://doi.org/10.1094/PHYTO-12-22-0455-PER

Interpretive Summary: Citrus greening disease is a fatal bacterial disease of citrus and is decimating citrus production in Florida. The disease is emerging in California, Texas, and other areas where citrus is grown. A meeting in May 2022 hosted by the California Citrus Research Board identified a need for the citrus greening research community to closely interact in sharing methods for screening antimicrobial peptides. In response to this need, the Office of National Programs at the U.S. Department of Agriculture (USDA) Agricultural Research Service (ARS) initiated a monthly HLB antimicrobial screening discussion group, including scientists from public and private universities, the US government, and grower consortia. Several projects funded by USDA NIFA are focused on crowdsourcing and streamlining antimicrobial screening efforts for the citrus industry, including an active NIFA project organized by the authors of this paper. Continued engagement and cooperation among the members of the scientific community in screening efforts will help ensure a solution is delivered to the citrus industry and maximize the impact of Federal and grower research funding allocations. This perspective article summarizes the scientific approaches available to researchers for screening therapies against citrus greening disease in the laboratory and makes recommendations on considerations for translational research approaches, such as field evaluation.

Technical Abstract: Huanglongbing (HLB), referred to as citrus greening disease, is a fatal bacterial disease impacting citrus production worldwide, in some areas resulting in devastation of the industry. As with all solutions to any crop production issues, a successful solution to HLB will be measured in economics: Citrus growers need treatments that improve tree health, fruit production, and most importantly economic yield. The profitability of citrus groves is the ultimate metric that truly matters when searching for solutions to HLB. Scientific approaches used in the laboratory, greenhouse, or field trials are critical to discovery of those solutions and to estimate the likelihood of success of a treatment aimed for commercialization. Researchers and the citrus industry use a number of proxy evaluations of potential HLB solutions and understanding the strengths and limitations of each assay as well as how best to compare different assays is critical for decision making to advance therapies into field trials and commercialization. This perspective aims to help the reader compare and understand the limitations of different proxy evaluation systems based on the treatment and evaluation under consideration. The researcher must determine the suitability of one or more of these metrics to identify treatments and predict the usefulness of these treatments in having an eventual impact on citrus production and HLB mitigation. As therapies advance to field trials in the next few years, a re-evaluation of these metrics will be useful to guide future research efforts on strategies to mitigate HLB and vascular bacterial pathogens in other perennial crops.