Factors affecting gene transformation in mangosteen

Factors affecting gene transformation in mangosteen (Garcinia mangostana L.) were investigated. Types of explants, strains and densities of Agrobacterium tumefaciens, and co-culture methods were examined to optimize gene transformation. The results showed that among strains of Agrobacterium tumefaciens tested, LBA 4404 containing pBI 121 gave the calli with the highest resistance to kanamycin. Kanamycin at the concentration of 50-100 mg/l was the best range for selection of transformants. Higher density of agrobacteria tended to promote higher frequency of transformation. The best co-culture method was dipping the explant in a solution of agrobacteria for 10 minutes, followed by culturing onto co-culture medium without antibiotic for 48 hours. Among the explants used to co- culture with bacteria, half leaf treatment gave the best result for transformation; however, callus proliferation and plantlet regeneration were inferior to whole leaf treatment. Activity of β-Glucuronidase (GUS) could not be detected, thus resistance to kanamycin was used for detecting transformability. Shoot primordia could be induced from kanamycin-resistant calli grown in regeneration medium. After maintenance by subculturing to the same medium 2 to 3 times in 2-3 months, the developed shoots turned brown and finally died. Hence, the transformed plant of mangosteen was not obtained from this experiment.