Genetic transformation has become a very effective tool in improving crops by incorporating genes for better agronomic characteristics, resistance to pests and diseases, and increased nutritional and food quality. This technology can also be advantageously used in improving fruit trees since a specific advantageous trait may be added to a given cultivar or rootstock genome while avoiding burdens of sexual recombination and involvement of deleterious characteristics. Genetic transformation of citrus genotypes has been difficult due to low-efficiencies and presence of non-transformable varieties.

A successful genetic transformation process involves the stable integration of foreign DNA into the host genome and the subsequent regeneration of whole plants from the transformed cells. A research team from Udayana University and Gajah Mada University in Indonesia attempted to genetically transform citrus through Agrobacterium tumefaciens. Internodal stem segments from citrus seedlings were cultured and inoculated with Agrobacterium tumefaciens harboring binary Ti plasmid vector that contained the genes for detectable marker ß-glucuronidase (GUS) and the selectable marker NptII. Results showed that shoots can be regenerated in media with 100 É g/ml kanamycin, and about 10 % of them contain the gusA gene. Some of the GUS+shoots were confirmed by polymerase chain reaction (PCR) analysis