Somatic Embryogenesis from the Leaf-Derived Calli of In Vitro Shoot-Regenerated Plantlets of Rosa hybrida ‘Carola’

Roses are one of the most important flowers applied to landscape, cut flowers, fragrance and food industries widely. As an effective method for plant reproduction, the regeneration via somatic embryos is the most promising method for breed improvement and genetic transformation of woody plants. However, lower somatic embryogenesis (SE) induction rates and genotypic constraints impede progress in genetic transformation in rose. This study describes a plant regeneration system for the famous red cut flower cultivar Rosa hybrida ‘Carola’. The stems without petioles cultured on Murashige and Skoog (MS) medium supplemented with 1.0 mg·L−1 6-benzylaminopurine (6-BA), 0.05 mg·L−1 a-naphthalene acetic acid (NAA) and 30 g·L−1 sucrose showed the maximum proliferation coefficient of shoots with 3.41 for the micropropagation system. We evaluated the effects of different plant growth regulators (PGRs) on the induction, proliferation and conversion of somatic embryos. The induction rate of calli reached 100% on MS medium supplemented with 2.0 g·L−1 NAA and 30 g·L−1 glucose. The highest induction rate of somatic embryos achieved a frequency of 13.33% on MS medium supplemented with 2.0 mg·L−1 zeatin (ZT), 0.1 mg·L−1 NAA and 30 g·L−1 glucose. The most suitable carbohydrate with 60 g·L−1 glucose resulted in a proliferation rate of somatic embryos (4.02) on MS medium containing 1.5 mg·L−1 ZT, 0.2 mg·L−1 NAA and 0.1 mg·L−1 gibberellic acid (GA3). The highest somatic embryos germination rate (43.33%) was obtained from the MS medium supplemented with 1.0 mg·L−1 6-BA, 0.01 mg·L−1 IBA and 30 g·L−1 glucose. Finally, the germinated somatic embryos successfully rooted on 1/2 MS medium containing 1.0 mg·L−1 NAA, 30 g·L−1 sucrose, and the vigorous plantlets were obtained after hardening-off culture. This study provided a stable and efficient protocol for plant regeneration via somatic embryos in R. hybrida ‘Carola’, which will be beneficial to the further theoretical study and genetic improvement in roses.