1. Please state project objectives and what work was done this quarter to address them:Objectives of this project are to determine the phytotoxicity of OTC and other potential partner antibiotics 1) by a citrus leaf assay in the lab (completed), 2) by a greenhouse assay in seedling trees (completed), and 3) to compare OTC with other antibiotics’ efficacy against CLas on mature trees in the grove (in progress). This quarter (Q3), we completed all injections on mature trees in the field, which corresponds to objective 3. All phenotypic tree measurements were taken, such as trunk diameter, canopy area, and height of each tree. We also recorded the visual parameters of citrus diseases that were present, which included HLB ratings, canker ratings, canopy color, and canopy density. Flower and new shoot formation percentages per tree were tracked to determine later if the treatment was potentially influencing/altering these parameters.We tracked all the points of injections (injection hole), one by one, and found no phytotoxicity (in terms of oozing or cracking) as of now. In general, no phytotoxicity was found on the last visit to the trial (dated 8.13.2024). Leaf samples were taken (one month after injection) and will be processed for CLas titers to compare with time zero. We will continue to sample other time points.Greenhouse phytotoxicity data (objective 2), collected during Q1 and Q2, were presented at the American Phytopathological Society’s annual Plant Health conference in Memphis, Tennessee, in July 2024. Per CRDF’s advisory request, we included additional treatment in our ongoing field trial. On August 12, we injected treatment consisting of kasugamycin +OTC (1/2 dose each; 5500 ppm) mixed together in the same FlexInjec injector (2 FlexInject per tree; 50 ml per FlexInject), as well as kasugamycin alone (1/2 dose; 5500 ppm), and OTC alone (1/2 dose; 5500 ppm) into mature Hamlin trees at the SWFREC trial site. 2. Please state what work is anticipated for next quarter:We will continue to sample leaves for CLas titers and process them to determine if a particular treatment significantly reduces CLas (using qPCR). Phytotoxicity will continue to be tracked every week. Visual and disease ratings, as well as canker incidence, will be tracked on a monthly basis. Flowers and shoots will also be counted together, along with the visual ratings. 3. Please state budget status (underspend or overspend, and why): We are paying the salary of one of the students who is working 60% on this project. The project is underspending as of now, but we anticipate being back on track soon. The reason that we are currently under budget is that a few of the most expensive antibiotics involved in the trial did not need to be purchased initially, as we had them on our hands to start. In the next couple of months, we will buy more of these antibiotics and use these funds.
1. Please state project objectives and what work was done this quarter to address them: This is a first year, third quarter report. The goal is to evaluate new anti-CLas compounds in Florida singly and in combination with OTC to determine their effects on HLB tree health, yield, and injury. The study objectives are: Objective 1: Pre-screening and quality control (purity, solubility, and bioactivity) of selected anti-CLas leads. (Initiated). Objective 2: Multi-year field evaluation of new chemicals, OTC, and combinations by trunk injections. (Initiated). Based on CLas-citrus hairy root effiacy assays (Irigoyen et al., 2020), we shortlisted five new active ingredients for which synthesis and sourcing in sufficient amounts needed for the field trials were completed. All quality control assays (solubility, bioactivity, dose determination) were completed. We aimed to dissolve all compounds in water to avoid using any other solvents on the trees. Three out of five compounds were fully soluble in water. Two were partially soluble. All the molecules were shipped to Dr. Albrecht lab. Trunk injections were conducted on ~7-year-old HLB-affected sweet orange (Valencia/US-897) trees at the UF/SWFREC, as per the experimental design. 2. Please state what work is anticipated for next quarter: In the next quarter, trees will be monitored for potential unintended injury or toxicity issues. General grove care and management activities will continue. Any changes in horticultural traits will be also monitored. 3. Please state budget status (underspend or overspend, and why): Ontrack with spending. 4. Please show all potential commercialization products resulting from this research, and the status of each: By the end of the study, we anticipate identifying one or more new active ingredients that improve the HLB-affected tree health and fruit yield. The new chemicals could be developed as commercial products singly or combined with OTC for HLB management.
1. Please state project objectives and what work was done this quarter to address them:This report is for year 3 (July 1, 2023 – May 30, 2024) of Project 21-002C – Continued Support for the Southern Gardens Diagnostic Laboratory. This project provides HLB testing for researchers, growers and homeowners. A total of 11,030 samples were run during the year. All samples were plant samples, mostly from research trials. To date, a total of 70,600 samples have been run for the 3 years that have been funded to date. The number of samples for year 3 represents a substantial reduction from the number of samples received in the past (averaging about 25,000/yr). This could be due to the state of the industry or to the perception that PCR analysis does not provide the resolution necessary to discriminate between treatments. As an attempt to provide more applicable data to determine if HLB mitigation treatments were working, SGDL is in the process of adapting and validating an assay developed by Dr. Ping Duan (USDA) to indirectly measure activity of the CLas bacterium. This assay, if validated, will be offered in the future as a means of evalutating treatments (e.g. OTC injection) to see if CLas metabolism and growth is being affected.2. Please state what work is anticipated for next quarter:SGDL will continue the testing and validation of the assay developed by Dr. Duan to determine it’s potential for use as a method to evaluate the effectiveness of HLB mitigation strategies. If it proves to be an effective method, this assay as well as the convential qPCR and qPCR with copy number determination will be offered to growers and researchers going forward.3. Please state budget status (underspend or overspend, and why):Due to the reduction in the number of samples and cofunding by one of the private companies that is utilizing the laboratory, the spending was well under the not to exceed cap that CRDF placed on the spending. Although the cost per sample went up (due to the fixed cost of the technicians being spread out over a smaller number of samples), the amount funded by CRDF was approximately 62% of the not to exceed cap.
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