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ARS Home » Pacific West Area » Riverside, California » National Clonal Germplasm Repository for Citrus » Research » Research Project #437386

Research Project: Ensuring Security and Integrity of Valuable Breeding, Research, and Germplasm Collections

Location: National Clonal Germplasm Repository for Citrus

Project Number: 2036-21000-011-29-R
Project Type: Reimbursable Cooperative Agreement

Start Date: Oct 1, 2019
End Date: Sep 29, 2020

Our goal is to protect valuable citrus germplasm collections from huanglongbing (HLB) and to evaluate early detection technologies (EDT). We will survey the collections with the canines, collect and assay plant tissue from canine alerted trees, negative control plants will come from the USDA ARS screen houses (ACP proof). Specific objectives include: 1. To survey citrus at UCR and UC-LREC for suspected HLB infected trees using canines and relate canine positives to other EDT methods and the time course of qPCR positives in California. 2. To assay research fields for HLB-associated pathogens and other relevant citrus pathogens. This encompasses trees of the genus Citrus and citrus relatives in the Aurantiodeae. 3. To increase the efficiency of large-scale surveys by incorporating early detection technologies with confirmation using USDA APHIS qPCR protocols.

UCR and USDA scientists intend to be proactive in maintaining and protecting the citrus germplasm field collections. Until we have the technology and ability to eliminate HLB, the first step in protecting these resources is to identify infected trees and not allow them to provide a source of inoculum for adjacent trees. This systems approach could be implemented by regulators and/or growers to quickly detect potential sources of infection, and to determine the area around qPCR positive trees that need to be removed and thus, rapidly respond and potentially stay ahead of disease spread. Proactive protection of valuable breeding and research collections secures the health status of valuable germplasm and breeding lines and protects collections for future generations. ARS scientists will survey and assay trees of citrus/citrus relatives for the presence of HLB-associated pathogens using the USDA APHIS qPCR protocols and other primers including the newly reported RNR primers (J.C. Chen 2016). Each tree identified as a dog alert will be sampled extensively (200 petioles or shoots) for qPCR analysis, in addition to petioles and shoots, we will assay roots from a limited number of trees. As a control, a tree of the same variety from the USDA ARA screen house would be sampled and similarly analyzed.