SP HLB-resistant rootstock candidates for the citrus industry: validating and understanding disease resistance
Research by: John Chater, Jude Grosser, Fred Gmitter, Liliana Cano, Yu Wang, Zhenyu Jia, and Manjul Dutt, all of the University of Florida
Article written by: John Chater
Article edited by: Ed Stover, Lukasz Stelinski, Peggy G. Lemaux
What is the technique?
This project will investigate candidate rootstock selections that do not test positive for CLas, the bacterium that causes huanglongbing (HLB), and/or appear resistant to HLB by first testing positive and then testing negative, seemingly eliminating CLas (Figure 1). Experiments will be conducted on inoculated plants in the greenhouse and inarching (grafting new rootstocks into established trees) experiments that will be conducted in an infected grove. ‘Valencia’ scions infected with HLB will be grafted on the rootstocks. The rootstocks will include several selections that are showing some level of resistance plus two industry-standard rootstocks. This project will gather horticultural data and multi-omic data (described below) to gain knowledge about the complex interactions leading to HLB tolerance and resistance. Horticultural data collected will include traits important to citrus production, including plant growth, plant health, number and size of leaves and length and diameter of shoots. Data will also be collected on HLB symptoms and attempts will be made to quantify huanglongbing bacterial titer levels to determine infection levels. The multi-omics data that will be collected include genomic (relating to genome DNA), transcriptomic (relating to RNA levels), and metabolomic (relating to biochemistry and metabolism) data.
How is that procedure involved in the research being described and what was discovered?
Leaves and roots of the scion and rootstock, respectively, will be sampled at three time points each year, over multiple years, to determine differences in gene expression and metabolomic profiles among the rootstocks used in this study. Movement between rootstock and scion of metabolites or RNAs, which may be implicated in the HLB disease response, will also be evaluated. The project is still in its early phases in April 2023 and growers will be updated as new discoveries are made.
Who is working on this project?
John Chater, Jude Grosser, Fred Gmitter, Liliana Cano, Yu Wang, Zhenyu Jia, and Manjul Dutt at the University of Florida are working on this project.
What are the challenges they are facing?
Challenges faced include sifting through “big data” sets and using that information in multi-omics models. Making sure plants are propagated well and successfully inoculated with infected budwood are early challenges in this study. With multi-omics data, sometimes it is a challenge to identify certain components. For example, with metabolomics, there are often molecules that are unknown and unclassified.
Funding source: United States Department of Agriculture, National Institute of Food and Agriculture
as though not infected with the HLB pathogen. Because it is not testing positive, and it is displaying a relatively high level of tree health, this genotype is one of the potentially HLB-resistant rootstocks selected for study in this project.