Assessment of grapefruit expressing anti-NodT antibody for huanglongbing resistance

Authors: VOSBURG, CHAD - Pennsylvania State University; SINN, JUDITH - Pennsylvania State University; ORBOVIC, VLADIMIR - University Of Florida; FERRAREZI, RHUANITO - University Of Georgia; ZAPIÉN MACÍAS, JOSÉ MARTÍN - University Of Florida; Taylor, Earl; Hilf, Mark; MCCOLLUM, GREG - Retired ARS Employee; Gottwald, Timothy; Stover, Eddie; MCNELLIS, TIMOTHY - Pennsylvania State University

Submitted to: PhytoFrontiers
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/19/2023
Publication Date: 1/31/2024
Citation: Vosburg, C., Sinn, J., Orbovic, V., Ferrarezi, R., Zapién Macías, J., Taylor, E.L., Hilf, M.E., Mccollum, G., Gottwald, T.R., Stover, E.W., Mcnellis, T.W. 2024. Assessment of grapefruit expressing anti-NodT antibody for huanglongbing resistance. PhytoFrontiers. 4:172-182. https://doi.org/10.1094/PHYTOFR-06-23-0078-R.
DOI: https://doi.org/10.1094/PHYTOFR-06-23-0078-R

Interpretive Summary: In this article, we examine if genetic resistance is an alternative to chemical management for HLB. A single chain variable fragment (scFv) that we predicted would inhibit CLas growth or HLB disease development was tested using three separate inoculation techniques to test for differences in HLB expression in Duncan grapefruit. The result was that the anti-NodT scFv antibody in grapefruit did not result in decreased HLB susceptibility. We are hopeful that this methodology will be useful in assessing citrus germplasm for HLB resistance.

Technical Abstract: Growers rely on broad-spectrum agrochemicals to manage one of the most economically important fruit tree diseases, huanglongbing (HLB, citrus greening disease), presumptively caused by the gram-negative bacterium ‘Candidatus Liberibacter asiaticus’ (CLas). While genetic resistance would be an attractive alternative to chemical management, this option is not yet available for HLB. Here, we tested whether a single chain variable fragment (scFv) antibody targeting the predicted CLas outer membrane transporter NodT can inhibit CLas growth or HLB disease development when expressed in ‘Duncan’ grapefruit (Citrus x paradisi). Wild type and scFv-expressing germplasm was challenged with CLas using three inoculation approaches: psyllid-mediated inoculation, vegetative graft inoculation, and natural exposure in grove-like conditions. With the first two approaches, HLB symptom expression and CLas bacterial titers in scFv grapefruit lines were not significantly different from wild type controls. In the grove trial, one scFv line exhibited a slight, but significant, reduction in canopy chlorosis compared to wild type controls. Wild type and scFv lines were similar in all other metrics. We conclude that expression of anti-NodT scFv antibody in grapefruit did not result in decreased HLB susceptibility. We hope that the methodology described here might be useful for those assessing citrus germplasm for HLB resistance in the future.