Testing grapefruit trees expressing an anti-NodT antibody for resistance to HLB

Testing grapefruit trees expressing an anti-NodT antibody for resistance to HLB

Report Date: 12/23/2020
Project: 18-016   Year: 2020
Category: Plant Improvement
Author: Tim McNellis
Sponsor: Citrus Research and Development Foundation

1. Please state project objectives and what work was done this quarter to address them: This report covers the period of September 1 – November 30, 2020.  The objective of this project is to test transgenic ‘Ducan’ grapefruit trees expressing an anti-HLB antibody fused to the FT (Flowering Locus T) protein.  Work on the project was slowed a bit by COVID-19 restrictions.  However, tissue sampling and phenotypic analysis was continued on three HLB inoculation tests underway for the FT-scFv plants:  a field trial natural inoculation; an Asian citrus psyllid (ACP) infection in the greenhouse; and a graft challenge with FT-scFv scions grafted to HLB-infected rough lemon rootstocks.  Samples taken from the field trial trees were all negative for ‘Candidatus Liberibacter asiaticus’ (CLas) infection by qPCR at the 6-month point after planting the trees at the test site in November of 2019.  Samples were taken and frozen for later analysis in November, 2020.  We applied for and received permission for travel by graduate student Mr. Chad Vosburg to Florida from  Pennsylvania to perform research at the Univerersity of Florida Indian River Research and Extension Center (IRREC) in Fort Pierce, FL.  This included permissions from Penn State and the University of FL.  To make this work possible, permission was applied for and recieved to transfer most of the citrus trees for this project from the next door United Sttaes Horticultral Research Laboratory (USHRL).  Trees were moved in part in November, 2020.  Photographic documentation of control and FT-scFv scions on HLB-infected rough lemon was performed in October, 2020.  We also applied for permits to move replacement trees from Florida to Pennsylvania for transgene protein expression and target interaction properties.  A no-cost extension was approved to extend the project operation period to the end of May, 2021.  2. Please state what work is anticipated for next quarter: Graduate student Mr. Chad Vosburg will visit IRREC for the first half of January,2021, to perform a replicate graft transmission experiment, which yielded promising results in the first run of the experiment.  He will also sample trees from the field site and the psyllid-mediated infection tests, test some of these for CLas levels by qPCR, and send a remainder of them to a centralized CLas quantification facility for analysis.  Trees will be transferred to our Pennsylvania lab for characterization of transgenic protein expression.  Quantitative CLas analysis in field-grown, graft-inoculated, and ACP-challenged FT-scFv plants and control plants will be obtained.  Plans will be made for a trip to Florida by Chad in May, 2021.  3. Please state budget status (underspend or overspend, and why):  Budget spending is on track, considering delays due to COVID-19.  We will submit an amended budget by January, 2021.  


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