Recovery of transgenic orchid plants with hygromycin selection by particlebombardment to protocorms

Protocorms of orchid (Dendrobium hybrid) were transformed by microprojectil e bombardment with a helium-pressured PDS 1000 particle gun. Gold particles coated with plasmid DNA containing ss-glucuronidase (GUS) and hygromycin p hosphotransferase (Hpt) marker genes were used. Potentially transformed tis sues were identified by active growth on MS medium supplemented with 50mg l (-)1 hygromycin. After 4-6 months of continuous selection, 15 hygromycin-re sistant lines were recovered. Integration of transgenes into the genome of the transformed protocorms and plantlets were confirmed by GUS histochemica l assay and Southern blot hybridization. The transgenic protocorms have gon e through propagation for more than 8 months and maintained their transgeni c characters. These results indicate that we have established a system for orchid transformation in a relatively high frequency and the transgenes are stably expressed in the transgenic plants.