Efficient transgenic plantlet regeneration from hairy roots via somatic embryogenesis and hardening plantlets of Panax vietnamensis by iron nanoparticles-supplied culture

In this study, the plantlet regeneration of Panax vietnamensis via somatic embryogenesis derived from hairy root callus was investigated. The results showed that the percentage of callus-induced hairy roots was 100 percent on SH medium supplemented with 0.5 mg/L NAA combined with 2.0 mg/L BA and 30 g/L sucrose after 6 weeks of culture. Callus was transferred to SH medium supplemented with 1.0 mg/L 2.4-D combined with 2.0 mg/L BA to induce somatic embryogenesis. The percentage of somatic embryogenesis callus was 100 percent, and the average number of embryos per sample was 63.7 embryos after 6 weeks of culture. The somatic embryos were then transferred to the plant growth regulators-free SH medium for the maturation. They developed progressively through the globular, heart, torpedo, cotyledon stages, and finally formed plantlets. PCR analysis revealed that plantlets derived from hairy roots retained the Ri T-DNA. The morphology of these plantlets were not different from the non-transformed plantlets as a control, but the root growth was better. Adding iron nanoparticles to the culture medium had improved the in vitro rhizome proliferation and growth of plantlets derived from hairy root, which supported plantlets survival when planted in the soil. This is the first report of transgenic plantlets regeneration from hairy roots in P. vietnamensis that shows the possibility of regenerating transgenic plantlets derived from hairy roots via somatic embryogenesis in high valuable medicinal plants.