AN EFFICIENT PROTOPLAST-TO-PLANT SYSTEM FOR THE HYBRID ORNAMENTAL SHRUB, WEIGELA X FLORIDA CV BRISTOL RUBY (CAPRIFOLIACEAE)

Strategies were developed for the successful isolation of large number s of highly viable protoplasts from the leaves, stems and roots of axe nic plants of the hybrid ornamental shrub Weigela x florida cv Bristol Ruby. Protoplasts, of all sources, were cultured on different media, leading to the establishment of sustained divisions, and coupled with the production of multi-celled (>50 cells) colonies, However, those co lonies derived from mesophyll protoplasts only were capable of a furth er proliferation to the callus stage. Upon transfer to a regeneration medium consisting of MS salts and organics plus a range of concentrati ons of NAA and BAP, such calli underwent caulogenesis, with optimum re sponses for a medium with 1.0 mg l-1 NAA and 1.0 mg l-1 BAP. The proto plast-derived shoots thus obtained were multiplied on MS medium with 0 .1 mg l-1 IBA, 0.5 mg l-1 BAP and 0.1 mg l-1 GA3. Individual shoots we re subsequently rooted on a half-strength MS medium plus 3. 0 mg l-1 I BA, and complete protoplast-derived plants were finally transferred to the glasshouse for acclimatization.