Development of a high-frequency in vitro regeneration system in Indian lotus (Nelumbo nucifera Gaertn.)

The Indian lotus (Nelumbo nucifera Gaertn.) is a popular ornamental plant and a source of traditional herbal medicine. Its various parts are widely used in the pharmaceutical, cosmeceutical, and nutraceutical industries. The recent study aimed to develop a high-frequency in vitro regeneration system in Indian lotus. This study utilizes the pink lotus cultivar from the Botanical Garden of CSIR-NBRI Lucknow. The study was successfully achieved through direct and indirect methods using different plant growth regulators (PGRs). A direct regeneration system was established using explants shoot apical meristem and plumule cultured on SIM supplemented with 17 combinations and concentrations of BAP and NAA. Both explants produced the highest number of shoots with a combination of 4.44 μM BAP and 0.55 μM NAA. The highest number of shoots per explant 25 ± 1.0 was developed from the shoot apical meristem, while the plumule explant developed 16.3 ± 0.5 shoots per explant. Thereafter, the plantlets were transferred to LRIM, which contained 17 combinations and concentrations of NAA or IBA and BAP. The maximum number of roots, per explant 23.6 ± 0.5, was developed from shoot apical meristem using 2.22 μM NAA and 0.54 μM BAP. The highest number of roots, per explant 23 ± 1.0, was developed from the plumule using 4.44 μM IBA. Indirect somatic embryogenesis has been established through callus culture. The leaf segments were cultured onto a callus induction medium supplemented with ten combinations of 2,4-D and BAP. The high-frequency callus formation 24.33 ± 0.5 was obtained with a 5.0 μM 2,4-D and 1.0 μM BAP combination. All developmental stages at the proembryo, globular, heart, torpedo, and mature embryos were formed on concentrations of 2,4-D and BAP. After inducing shoot and root growth, well-developed plantlets were transferred to the greenhouse, resulting in a success rate of 18.47%.