The purpose of this project is to reveal the mechanisms of bactericide uptake and transport in citrus plant and establish a theoretical basis for developing technologies to improve the efficacy of bactericides, which is helpful to provide potential solution to the development of effective chemotherapeutic tools for HLB management. Achieving this outcome will require progress in the following three tasks: (1) to compare the delivery efficacy of bactericides with three application methods (foliar spraying, truck injection, and root administration) based on the uptake and dynamic movement/distribution of the bactericide within the tree; (2) to clarify the systemic movement and transportation mechanisms of bactericides within the phloem of tree; and (3) to investigate the effects of citrus variety and age on the delivery efficacy of bactericides. This project requires a combination of greenhouse studies and field trials. Prior to conducting these experiments, a sensitive and accurate quantifying method of bactericides (oxytetracycline and streptomycin) in citrus tissues is needed. This project officially started on December 1, 2018. This is the 4th quarterly progress report covering 9/01 to 11/31, 2019. During this period, we have conducted and/or completed the following work/research tasks:
1) The procedures of sample preparation method are further improved. Based on the test results of leaves, stems and root samples from foliar spraying, the recovery of both bactericides (streptomycin, oxytetracycline) is approximately 70%, which is within the acceptable range.
2) The greenhouse experiments of citrus tree trunk injection were completed. All the samples were collected and are being prepared with the above-mentioned newly modified method for the analysis of bactericides using a LC-MS. The results are expected to be available at the end of December 2019.
3) The root administration experiments were initiated in greenhouse, and the treatments included two bactericides (streptomycin, oxytetracycline) and three different concentrations for each bactericide on young citrus trees. So far, two batches of samples (leaves, stems and root) were collected and are being prepared for the analysis of bactericides using the LC-MS, and the last batch of samples will be collected on December 20.
The work planned for the next quarter:
The major goals of research for the next three months are to analyze the obtained data and to evaluate the delivery efficacy of three different application methods for bactericides in field. To accomplish the goals, field experiments will be carried out and the following research tasks will be performed during the next quarter (December 1, 2019 to February 29, 2020): 1) Collection and analysis of the obtained data; 2) Selection of desired sites and citrus trees for field experiments; 3) Conducting foliar spraying treatments of both bactericides for the field experiments.