Citrus is one of the major horticultural cash crops in the Southern United States. Several attempts have been made to genetically improve present citrus cultivars using biotechnology. We report transformation of citrus (Citrus sinensis (L.) Osbeck `Hamlin') suspension cultures using microprojectile bombardment.
A thin layer of seven day-old suspension cultures, grown in HH medium, were transferred to Whatman #1 filter paper at a cell density of 0.15 mg/ml fresh weight. The cells were bombarded with 1.112μM diameter, DNA-coated, tungsten particles using the Dupont PDS 1000 biolistic system. Plasmid PRT 99 GUS containing the marker genes β-Glucuronidase (GUS) and NPT II, with a 35S promoter, and NPT II terminators was used in transformation.
GUS activity was monitored on a time scale. Expression of GUS was observed after 48 hours of bombardment. Further studies are being done to enhance the transformation efficiency.