Rescue and Preservation of Citrus Germplasm Threatened by Huanglongbing and Citrus Canker

Huanglongbing (HLB)and Asiatic Citrus Canker (ACC) diseases are now endemic in Florida and are having devastating impact on the Florida citrus industry as well as the  USDA citrus breeding program.  HLB became established among numerous promising hybrids at the USDA–USHRL farm in St. Lucie County, Florida, and in trees at the A.H Whitmore Florida Citrus Research Foundation Farm in Lake County, Florida.  ACC is also present in the St. Lucie Co. site, but as yet not at the Lake Co. site.  Many of the trees impacted by these diseases exist only in our populations of segregating hybrids in the field or in a virtually irreplaceable germplasm collection. Starting with the discovery of ACC at the St. Lucie county site, we began a concerted effort to rescue our most elite material from the field. This effort started with moving selected trees to an out of state location to avoid the ACC eradication effort. Following confirmation of HLB at the St. Lucie county site, we began experiments to determine if we could eliminate the HLB pathogen from trees of value to our program. We have investigated a number of protocols, including selective grafting, use of antibiotics and cryopreservation treatment. This presentation will review our successes at rescuing citrus germplasm.