Plant Regeneration via Somatic Embryogenesis and Indirect Organogenesis in Blue Honeysuckle (Lonicera caerulea L.)

Blue honeysuckle (Lonicera caerulea L.), which belongs to the Caprifoliaceae family, is an emerging fruit crop worldwide. For the development of a transgenic system and multipurpose tissue culture, this study for the first time established an in vitro regeneration system via somatic embryogenesis, as well as improving the previously established indirect organogenesis-based regeneration system. For embryogenesis, Murashige and Skoog (MS) medium supplemented with 1.0 mg/L 2,4-dichlorophenoxyacetic acid (2,4-D) showed the highest induction rate of the embryogenic callus (97.6%), and MS supplemented with 0.1 mg/L 6-benzyladenine (6-BA), 0.1 mg/L alpha-naphthaleneacetic acid (NAA), and 0.5 g/L activated carbon (AC) achieved the highest somatic embryo rate (28.3%). For indirect organogenesis, MS medium supplemented with 1.0 mg/L 6-BA and 0.1 mg/L NAA resulted in the highest non-embryogenic callus induction rate (98.9%) and adventitious shoot induction rate (51.6%). For adventitious root induction, MS supplemented with 1.0 mg/L indole-3-butyric acid (IBA) achieved the highest root induction rate (96.0%) and average root length (4.6 cm), whereas MS supplemented with 0.5 mg/L indole-3-acetic acid (IAA) resulted in the highest average regenerated root number (8.8). The total time for the regeneration from explants to soil-planted seedlings (10 euphylla) was 105 and 150 days with an efficiency of 44.1% and 23.9% through organogenesis and somatic embryogenesis, respectively. This study provides a powerful tool for rapid propagation, proliferation, and transformation, as well as laying a technological foundation for gene function research and genetic improvement of blue honeysuckle.