Somatic embryogenesis in miniature potted rose (Rosa hybrida L.).

Regeneration via somatic embryogenesis was established for the miniature rose cultivar (Rosa hybrida L. 'Linda'). Initially, in vitro cultures of eight miniature rose cultivars were established and then sufficient amounts of callus were produced on MS-media containing high levels of 2,4-D. Embryogenic callus was induced on calli of six cultivars incubated on media containing either zeatin or thidiazuron (TDZ). Although the frequency of somatic embryogenesis in 'Linda' was only 3.3%, further work on transformation was continued with this cultivar, because of promising results on plant regeneration. ABA was used for proliferation of embryogenic callus, and high concentrations of BAP combined with low concentrations of NAA and GA 3 were used for shoot regeneration and elongation. The observed high demand of auxin for callus induction and of BAP for shoot regeneration appeared to be due to low endogenous concentrations of these hormones in miniature roses. Shoots were rooted on 1/2 MS medium supplemented with IAA and IBA and transferred to the greenhouse. Plants flowered after about 10 weeks and were morphologically indistinguishable from the original plant.