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ARS Home » Southeast Area » Fort Pierce, Florida » U.S. Horticultural Research Laboratory » Subtropical Insects and Horticulture Research » Research » Research Project #435976

Research Project: High-Throughput Inoculation of Citrus Germplasm for HLB Resistance Screening

Location: Subtropical Insects and Horticulture Research

Project Number: 6034-22320-007-06-R
Project Type: Reimbursable Cooperative Agreement

Start Date: Jan 1, 2019
End Date: Dec 31, 2021

Objective:
1. To inoculate new transgenic and conventional citrus developed for huanglongbing (HLB) tolerance or resistance. 2. Support other projects targeting Asian citrus psyllid (ACP), Candidatus Liberibacer asiaticus (Clas) or vector and host relations by providing (as available) to researchers psyllids infected by the huanglongbing (HLB) pathogen.

Approach:
The basic huanglongbing (HLB) inoculation program is as follows. Psyllids for inoculations are obtained from psyllid colonies maintained on HLB-affected citrus in cages. Each cage of infected psyllids is considered a colony, and these colonies are regularly assessed to verify they contain infected psyllids, to estimate percentages of psyllids infected, and to assess levels of Candidatus Liberibacter asiaticus (CLas) present using quantitative polymerase chain reaction (qPCR) analyses. We maintain up to individual colonies in walk-in environmental chambers). To screen citrus for resistance to HLB, plants replicated for individual transgenic events or other genotypes of interest are caged individually and 20 psyllids from an infected colony are introduced into each cage. Multiple replicated sets of control plants are included in each trial to provide a baseline for identifying resistant types. The caged plants are maintained in one of two laboratories under ambient conditions beneath LED illumination (14 hours). After two weeks, the cages are removed and the plants are transferred to the breeders to be monitored for the disease and disease resistance/tolerance. The plants are transplanted to larger pots and moved to a psyllid-free hoop house to be evaluated for growth, HLB-symptoms and titer of the HLB pathogen. Eventually the trees are transplanted to the field for continued assessments.