|Williams, Timothy - UNIVERSITY OF CALIFORNIA|
Submitted to: HortScience
Publication Type: Abstract Only
Publication Acceptance Date: June 15, 1990
Publication Date: September 15, 1990
Citation: WILLIAMS, T.E. EX-SITU PRESERVATION, MAINTENANCE, AND EVALUATION OF VIRUS-FREE CLONAL CITRUS GERMPLASM. HORTSCIENCE. 1990. Technical Abstract: The USDA-ARS National Clonal Germplasm Repository for Citrus is establishing a virus-free clonal collection of 830 citrus germplasm accessions at its Riverside, California facility with the objective of reducing genetic vulnerability of citrus and providing virus-free clonal germplasm to researchers worldwide. Accessions in the collection are evaluated for trueness-to-type using leaf isozymes and are characterized for 58 descriptors. Research is expanding into RFLPs for development of a usable genomic map and cultivar-specific probes. Citrus seed, pollen and buds are being investigated for extended preservation under low temperatures and cryostorage. Preliminary data is promising but indicates considerable variability between cultivars. In-vitro culture of excised embryo tissue is being investigated. A comprehensive pathogen detection program is underway. Infected accessions receive shoot-tip micrografting and thermotherapy treatments to eliminate pathogens. Accessions are maintained as potted trees in greenhouse or aphid-proof screenhouses. A complete computer based record is maintained for each accession on site and in the USDA-ARS GRIN database.