Somatic embryogenesis and plant regeneration in Floribunda rose (Rosa hybrida L.) cvs. Trumpeter and Glad Tidings

Somatic embryogenic callus was initiated from in vitro-derived petiole and root explants, but not leaves, of the Floribunda rose cultivars Trumpeter and Glad Tidings following repeated subculture of callus on Schenk and Hildebrandt (SH) medium containing 2,4-dichlorophenoxyacetic acid (2,4-D). The use of a high auxin pretreatment increased the frequency of somatic embryogenesis, whilst l-proline, as a media supplement, had a critical role in enhancing somatic embryogenesis in the early stages of culture but increased the frequency of abnormal embryo formation when used in the later stages of culture. Maturation of somatic embryos was achieved by transfer to SH medium with reduced concentrations of 2,4-D and incorporation of abscisic acid (ABA) and 6-benzylaminopurine (BAP). The use of SH medium containing BAP and indole-3-butyric acid (IBA) facilitated embryo germination which was also enhanced by cold treatment. Phenotypically normal plants were recovered from germinated somatic embryos and successfully transferred to the glasshouse for flowering.