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ARS Home » Pacific West Area » Wapato, Washington » Temperate Tree Fruit and Vegetable Research » Research » Research Project #444424

Research Project: Identification of new ‘Candidatus Liberibacter solanacearum’ Haplotypes and Their Psyllid Vectors and Plant Hosts in the Northwest United States

Location: Temperate Tree Fruit and Vegetable Research

Project Number: 2092-21220-003-001-I
Project Type: Interagency Reimbursable Agreement

Start Date: Jun 1, 2023
End Date: May 31, 2024

The goal of this project is to reassess the actual diversity of Lso pathogens in the Northwest U.S. and to identify the psyllid vectors and respective plant hosts that contribute to epidemiology of these different pathogens. We have three objectives: 1) Identify known and currently unknown genetic variants of Lso by assaying psyllid specimens collected from vegetable and potato growing regions in Oregon and Washington State; 2) Identify developmental and feeding hosts of infected psyllids by identifying plant DNA harbored by infective psyllids (=“dietary history”), use that dietary information to pinpoint plant taxa likely to be harboring Lso, and field-examine suspect plant species for presence of Lso-infection and presence of Lso-infected psyllids; and 3) Prepare the findings in a formal report for APHIS and for peer-reviewed publications in scientific journals.

Objective 1. Psyllid specimens will be collected from sticky card traps and specialized psyllid traps which accumulate specimens directly into preservative. These traps will be placed along potato, vegetable, and seed crop fields in Central Washington State and in southern Oregon. Psyllids will be identified to species or genus and tested for Lso using established conventional PCR methods. If Lso is detected in any specimen, further identification of the Lso haplotype will be conducted by targeting of the 16S ribosomal RNA, 50S ribosomal protein subunits, and outer membrane protein for PCR and sequence analysis. DNA sequences will be submitted to GenBank. Objective 2. Psyllid specimens found to harbor Lso will undergo additional molecular work to determine what plant DNA (to species or genus taxonomic level) is harbored by specimens. PCR will be used to target the internal transcribed spacer (ITS) and chloroplast trnF genes. PCR products will be sequenced using the PacBio platform to identify plant species matches. Field verification of the gut contents work will be done by collecting psyllids from suspect plant species and testing them for Lso-presence. Leaf tissues of targeted plants will also be collected and tested for Lso infection. Objective 3. Findings from this study will be reported at the conclusion of this project to APHIS. Discoveries and descriptions of new Lso haplotypes, their psyllid vectors, and plant hosts of the pathogens and vectors will be published in scientific journals. DNA sequences for newly discovered Lso haplotypes will be submitted to GenBank. All cooperators will contribute to the writing of manuscripts, under the direction of the PI. Funding for this work will be acknowledged in all publications.