Pre-incubation of somatic tissues of the cut rose 'Carefree Beauty' and miniature roses 'Red Sunblaze' and 'Baby Katie' in 10, 100, or 200 #M 2,4-D induced the development of highly rhizogenic callus. Upon transfer ofrhizogenic callus to a regeneration medium containing 23 #M TDZ and 3 #M 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/zM 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 #M 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.

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The activity of a predicted promoter, PMC8, from Milk vetch dwarf virus was evaluated by comparing it with the cauliflower mosaic virus 35S RNA promoter (P35S) and PNCR, a promoter from Soybean chlorotic mottle virus. When the GUS fusion gene was introduced into tobacco, PMC8 showed a similar expression profile to P35S but with a more intense expression in proliferating tissues. The usefulness of PMC8 was confirmed by driving NPTII for selection of kanamycin-resistant tobacco plants with improved transformation efficiency. PMC8 was also effective in transgenic rice plants. Thus, PMC8 is useful as an alternative to P35S in both dicotyledonous and monocotyledonous plants, especially for gene expression in proliferating tissues.