Skip to main content
ARS Home » Pacific West Area » Riverside, California » National Clonal Germplasm Repository for Citrus » Research » Research Project #431619

Research Project: Protection of the USDA/ARS and UCR Citrus and Date Palm Collections from Pests and Disease through Cryopreservation Technologies

Location: National Clonal Germplasm Repository for Citrus

Project Number: 2036-21000-011-002-S
Project Type: Non-Assistance Cooperative Agreement

Start Date: Sep 1, 2016
End Date: Aug 31, 2021

The objective of this research is to hasten the back-up of the citrus collections by cryopreserving germplasm and testing for viability and presence of pathogens upon recovery of cryo-exposed tissues. Preliminary data from research projects intended to develop early detection methods for huanglongbing (HLB) (aka citrus greening disease) suggest trees infected with HLB-associated bacteria may be in the vicinity of the USDA/ARS and UCR citrus variety collections and the UC Citrus Clonal Protection Program, thereby threatening the health of these collections. There are over 2000 accessions of the genus Citrus and Citrus relatives housed within protective structures and in field plantings in Riverside and Exeter, California. These collections are composed of both commercially important varieties and diverse germplasm used for breeding purposes; some of which may contain disease and pest resistant genes. This valuable genebank must be preserved before HLB becomes widespread. Currently there are space, cost and labor limitations to maintaining every accession within a protected structure as required by federal and state regulatory officials. It is paramount to have an additional backup source for these valuable accessions and cryo-preservation is an economical and safe strategy to achieve this goal.

The citrus collections include about 2000 accessions, 500 of which are designated high priority and are maintained clonally in an NPGS insect-proof screenhouses in Riverside and on the UC Lindcove Research and Extension Center in Exeter, CA. These accessions have been pathogen-tested and are believed to be ‘clean.’ Proposed work will support the cryopreservation of shoot tips from 350 of the 500 accessions. In addition, the PI and ARS scientist are collaborators on a USDA APHIS MAC project through which citrus material is brought into California from Florida for evaluation under California growing conditions while it is undergoing investigation for HLB resistance and/or tolerance in Florida. This germplasm will also be slated for cryopreservation. A subset of these will be tested for viability and presence of contamination in culture and further indexed for the presence of pathogens. The UCR PI provides expertise in plant pathology and pathogen detection and will contribute training and oversight on laboratory analyses for plant pathogens. In addition, he will provide germplasm for cryo-preservation from his collection of disease-free commercially important citrus cultivars. The USDA ARS scientists are responsible for genetic resource management and will contribute the expertise in the preparation of material for cryopreservation. This collaboration is mutually beneficial in that both parties are interested in genetic resource collections and long-term preservation of germplasm viability. The longer term impact of this collaborative project will be a cryopreserved collection of citrus genetic resources that is disease-free and protected from future disease transmission. We also expect more efficient methods to evaluate germplasm viability and detect the presence of pathogens in genetic resource collections.