An efficient genetic transformation system is a preparation for Rosa multi-flora Thunb. var. cathayensis Rehd. et Wils to diversify its flower color through ge-netic engineering. We firstly optimized the explants and culture conditions on callus induction, hormone concentrations and dark period of culture time on bud differentia-tions in particular, with sterilized seedlings to establish the regeneration system of R. multiflora. It showed that callus induction frequency reached 100% after the ex-plants being cultured in dark for 21 d when MS was chosen to be the initial culture medium. The bud differentiation rate was 48% after cal i being cultured under dark for 8 d on MS medium supplemented with TDZ （1.5 mg/L） and NAA （0.05 mg/L）. The cal i was used as the explants that were infected with Agrobacterium tumefa-ciens harboring a DFR-RNAi construct. The transformation rate reached as high as 50%. The establishment of a highly efficient rose gene transformation system out-lined in this report is prerequisite for genetic improvement in rose flower colors.
