EN
Oncidium is a popular ornamental orchid and is produced as a high value cash crop for cut flower sold worldwide. Genetically transformed plants of Oncidium were regenerated after cocultivating protocorm-like bodies (PLBs) with Agrobacterium tumefaciens strain LBA4404 harboring pBI121 with OMADS1. The chopped PLBs precultured for 3 days in darkness produced more kanamycinresistant PLBs. G10 medium containing 200 mg l⁻¹ kanamycin was effective for the selection of transformed lines at a frequency of 9%. The rooted plantlets were transferred to pots, acclimated for 3 weeks in the culture room and then moved to the greenhouse. OMADS1 transgene was detected in transgenic lines by PCR, Southern blot analysis and RT-PCR were performed, and the results confirmed that OMADS1 was expressed in these 35S::OMADS1 transgenic plants. CaMV35S::OMADS1 transgenic Oncidium orchid plants flowered significantly earlier, produced more flowers and pseudobulbs than nontransgenic plants. The flower organ conversions were not observed in 35S::OMADS1 transgenic flowers of Oncidium. This is the first report on the ectopic expression of MADS box gene in O. Gower Ramsey using a simple and efficient gene transfer protocol.