Organogenesis and somatic embryogenesis in callus cultures of Rosa hybrida and Rosa chinensis minima

Pre-incubation of somatic tissues of the cut rose 'Carefree Beauty' and miniature roses 'Red Sunblaze' and 'Baby Katie' in 10,100, or 200 μM 2,4-D induced the development of highly rhizogenic callus. Upon transfer of rhizogenic callus to a regeneration medium containing 23 μM TDZ and 3 μM GA₃, a low frequency of shoot organogenesis (3.3%) and somatic embryogenesis (6.6%) was observed. Incubation of leaf and stem internodes in 11, 27, 54, 81, or 108 μM NAA followed by transfer of explants to the regeneration medium resulted in up to a 25% increase in shoot organogenesis from callus-derived internodal explants of 'Red Sunblaze', but no somatic embryogenesis was observed. The influence of glucose versus sucrose in the regeneration medium on leaf explants of 'Carefree Beauty' and 'Baby Katie' pre-incubated in 100 μM 2,4-D revealed a difference in genotypic response to shoot organogenesis and somatic embryogenesis. For 'Carefree Beauty', a concentration of 111 mM glucose induced higher frequencies of both organogenic (33%) and embryogenic calluses (25%) than either 59 mM or 117 mM sucrose. For 'Baby Katie', no significant difference was found for number of organogenic calluses induced on 59 mM sucrose and 111 mM glucose.