1a. Objectives (from AD-416):
1. Identify and prioritize valuable sources of citrus germplasm in Florida which are threatened by HLB or citrus canker. 2. Establish the selected germplasm at USDA ARS Ft. Pierce and subject to standardized thermotherapy procedures. Following thermotherapy of germplasm, test for diseases which should be eliminated, including HLB and citrus canker. 3. Once thermotherapied germplasm has tested free HLB and citrus canker and other pathogens which should be eliminated, budwood would be shipped to NCGRCD, Riverside where it would be subjected to shoot tip grafting, followed by biological and laboratory indexing to ensure elimination of all citrus graft transmissible pathogens as required for release from quarantine in NCGRCD by CDFA and USDA APHIS. 4. Germplasm released from quarantine at NCGRCD would be sent to FL Citrus Introduction Program which will test the repatriated germplasm via protocols established by the “Citrus Passport” protocol, and release to the industry, keeping a clean source in the DPI facility in Chiefland.
1b. Approach (from AD-416):
A committee composed of members from the citrus breeding teams from University of Florida, USDA ARS, Florida Budwood Program, NCGRCD, and members of the Florida Citrus Production Managers Association, Florida Nurserymans’ Association, and Florida Citrus Mutual would identify and prioritize elite germplasm vital for the short and long term survival of the Florida citrus industry and which is threatened by presence of exotic diseases. A technician, under the supervision of research scientists, would establish the plants and conduct the thermotherapy at ARS, Ft. Pierce, Florida. Personnel from ARS, Riverside and Florida CIP would conduct laboratory testing on plants at Ft. Pierce following the growout after thermotherapy. Once freedom from HLB and citrus canker is confirmed, budwood would be shipped under quarantine to the Repository, Riverside and some to Florida CIP, Gainesville, where shoot tip grafting followed by full biological indexing would be performed. Following release from quarantine, pathogen-tested budwood would be returned to Florida with a plant maintained in the Protected Collection at the Repository.
3. Progress Report:
This is the final report for this research. The purpose of this project is to preserve citrus germplasm in Florida that is threatened by loss due to huanglongbing (HLB) and citrus canker and relates to objective 1 of the parent project, "Strategically expand and improve collections of priority genetic resources of citrus and date palm and associated information". This research is in cooperation with the USDA ARS U.S. Horticultural Research Laboratory, Ft. Pierce, Florida, and the Florida Citrus Germplasm Introduction Program. Presently 66 accessions are being held at Ft. Pierce. These accessions have been subjected to antibiotic therapy, and are testing negative for Las by quantitative polymerase chain reaction assay. In collaboration with the Florida Citrus Germplasm Introduction Program, the accessions are beginning thermotherapy, which will be conducted for a 16 week time period. Following the thermotherapy, the accessions will be tested using laboratory methods for Candidatus Liberibacter asiaticus (Las) as well as other graft transmissible diseases of citrus, including viroids. Following the testing and depending on the results, the accessions will be forwarded to the USDA ARS Repository in Riverside for further clean up and testing before release from quarantine. The Repository, Riverside has already received 22 accessions from Florida, and 11 are nearing completion of therapy and indexing for release from quarantine status, and will receive the additional 66 accessions following thermotherapy treatment in Florida.