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ARS Home » Northeast Area » Beltsville, Maryland (BARC) » Beltsville Agricultural Research Center » Molecular Plant Pathology Laboratory » Research » Research Project #432613

Research Project: Development of Standard Positive Controls for Diagnostic Testing of Citrus

Location: Molecular Plant Pathology Laboratory

Project Number: 8042-22000-301-02-I
Project Type: Interagency Reimbursable Agreement

Start Date: Oct 1, 2016
End Date: Sep 30, 2017

Objective:
The Exotic Pathogens of Citrus Collection is the largest collection of clonally propagated pathogens of citrus in the world. It is part of the USDA ARS research program in the Molecular Plant Pathology Laboratory, Beltsville, MD. This project conducts research on high impact graft-transmissible and other pathogens of citrus, and develops diagnostic tests that can be applied to ensure that high quality citrus propagative material will continue to be produced, maintained, and supplied to scientists and the industry throughout the USA under the standards of excellence established by the National Clean Plant Network (NCPN). In Maryland, the Exotic Pathogens of Citrus Collection maintains a comprehensive and curated collection of graft transmissible pathogens of citrus, as well as a large collection of strains of Xanthomonas citri. The collection is used within the USDA ARS Molecular Plant Pathology Laboratory to develop sensitive and specific diagnostic tests for these pathogens. The tests are made available to the public at large and to the citrus clonally propagated germplasm community in particular to be implemented to safeguard to bud wood distributed to growers. Novel and widely used PCR-based diagnostic assays for Xanthomonas citri, Xylella fastidiosa, ‘Ca. Liberibacter asiaticus’ have been developed using the collection of the EPCC. This has been especially crucial since the introduction of Huanglongbing (HLB), one of the deadliest citrus diseases into Florida (2005), Texas (2008) and California (2012).

Approach:
EPCC currently maintains in planta collections of graft transmissible pathogens of citrus in 3264 sq ft of high quality greenhouse space, rigorously designed built, maintained and dedicated for the purpose. The facility is capable of maintaining citrus in Maryland year round. The facility is maintained in Maryland to protect the citrus industry from the pathogens. The EPCC maintains ~440 pathogen accessions, which includes accessions of citrus tristeza virus of all genotypes from 33 different countries. Most of these are not available anywhere else in the United States. The EPCC also includes accessions of the Citrus chlorotis dwarf virus (CCDV; Monopartite Begomovirus, obtained from Turkey) and Citrus yellow mosaic virus (Badnavirus, obtained from India). EPCC also maintains a collection of isolates of ‘Ca. Liberibacter asiaticus (HLB) obtained from Florida, California, South Africa, France, Thailand and Taiwan. The EPCC also maintains a collection of strains of Xylella fastidiosa subsp. pauca (Citrus Variegated Chlorosis (CVC); Brazil) and Xanthomonas citri (citrus canker; worldwide). The EPCC is currently working with a global network of researchers to characterize and develop molecular diagnostics for the complex of mite transmitted viruses that causes citrus leprosis disease. These accessions are used for the development and validation of assays for their detection. The current proposal will result in improved management and maintenance of the collection and enable nucleic extracts or non infections plant extracts to be made available to the CCPP, NCGRCD and researchers focused on the development of novel diagnostic methods for citrus pathogens at the University of California (Riverside and Davis), University of Florida, USDA ARS and USDA APHIS. The proposal will also result in the longer term in normalization of sanitizing and testing protocols to facilitate transfer of sanitized, pathogen-tested, horticulturally true-to-type materials among the clean plant centers.