Location: National Clonal Germplasm Repository for Citrus
Project Number: 2036-21000-012-031-I
Project Type: Interagency Reimbursable Agreement
Start Date: Oct 1, 2025
End Date: Sep 30, 2026
Objective:
Objective 1: Variety Introduction under Quarantine. Citrus germplasm identified by stakeholders or center management will arrive at NCGRCD quarantine facilities and be held under permit.
Objective 2: Disease Diagnosis & Pathogen Detection. Laboratory and biological testing of citrus germplasm will be carried out at the NCGRCD facilities prior to therapeutics to assess pathogen status and after therapeutics to determine effectiveness of the therapeutics. New and modified diagnostic protocols will be implemented as they become available.
Objective 3: Therapeutics of Citrus Propagative Material. Therapeutics for the elimination of citrus pathogens (shoot-tip grafting, heat therapy) will be carried out at the NCGRCD facilities.
Objective 4: Foundation Materials. Clean citrus accessions maintained in protective structures will be observed and repropagated as necessary. Trees will be horticulturally managed for optimum health and propagule production. Protected accessions will be retested to meet State and Federal standards and as otherwise determined to be necessary by center management. Seed source trees in the field will be re-tested to meet State standards. When sufficient material is available or newly sanitized, it will be sent to USDA-ARS National Laboratory for Genetic Resource Preservation for secure, long-term cryopreservation. Clean citrus propagative material will be distributed upon request to qualified institutions and individuals.
Objective 5: NCPN-Citrus-Administrative Activities. The Center Director will participate as a member of the Tier 2 in meetings of that body.
Objective 6: Education & Outreach Program Coordination. The Center Director is a member of the Education and Outreach Sub-Committee. He also participates in ad hoc education and outreach activities, upon request by NCPN, or in conjunction with educational activities.
Approach:
Objective 1. Variety Introduction under Quarantine. Citrus importation and cleanup are performed under PCIP_588-23-250-15452 (renewed 2024-08), which is on file at USDA-APHIS-PPQ Permits Unit and with CDFA. The method followed is summarized as follows: initial pathogen testing to determine incoming pathogen status, followed by therapeutics (shoot-tip grafting or thermotherapy). After therapeutics, the resultant plants are screened by laboratory testing, after which a select plant of each genotype is indexed biologically, followed by final lab tests. Plants testing negative for all known graft transmissible pathogens are petitioned to be released from quarantine.
Objective 2. Disease Diagnosis & Pathogen Detection. NCGRCD utilizes two basic types of diagnostics: laboratory-based and classical biological indexing. Laboratory tests are mostly qPCR, but ELISA is used for some re-testing purposes and culturing is used for a specific bacterial pathogen, Spiroplasma citri. Complete protocols are on file. A pipeline using NGS for pathogen testing has been developed and supplements the standard tests.
Objective 3. Therapy of Citrus Propagative Material. NCGRCD utilizes two therapeutic methods: shoot-tip grafting (STG) and thermotherapy. The emphasis is currently on STG but occasionally thermotherapy is still used.
Objective 4. Foundation Materials. Clean plants are maintained in a PPQ-approved protective structure under compliance agreement HLB-0082. The facilities are inspected by USDA-APHIS monthly for structural integrity and vector absence. Plants are retested as appropriate by NCGRCD personnel or in the case of HLB, by the California Department of Food and Agriculture Diagnostic Laboratory. Plants are inspected by unit personnel for insect pests & treated as necessary. Plants are repropagated as needed based upon observations by the staff. Other management practices are taken to ensure vigorous growth & production of budwood. When appropriate, budwood is removed from the trees and sent to the National Laboratory for Genetic Resource Preservation (NLGRP) for long-term preservation under the protocol developed at NLGRP. Clean plant propagative materials are distributed upon request. All pertinent phytosanitary regulations at all administrative levels are followed and appropriate documentation accompanies each shipment. Further information is available in NCGRCD Operations Manual draft.
Objective 5. NCPN-Citrus-Administrative Activities. The Center Director is a member of the Tier 2 board and Education-Outreach Subcommittee. He participates in meetings unless otherwise compromised. In addition, he participates in outside meeting activities of the Tier 2 as appropriate.
Objective 6. Education & Outreach Program Coordination. The Center Director is a member of the Education and Outreach Committee and participates in meetings unless otherwise compromised. He also participates in other ad hoc outreach activities or upon request.