Preserving Nature’s Treasure: A Journey into the In Vitro Conservation and Micropropagation of the Endangered Medicinal Marvel—<i>Podophyllum hexandrum</i> Royle

<i>Podophyllum hexandrum</i> Royle, also known as <i>Podophyllum emodi</i> Wall, holds significant ecological, ornamental, and medicinal values. However, it has become endangered due to overexploitation, prolonged seed dormancy, slow natural regeneration, and climate change. This study developed an efficient in vitro protocol for callogenesis and micropropagation of <i>P. hexandrum</i> to conserve germplasm in in vitro conditions. Callus formation from various plant parts, including the leaf, stem, rhizome, radicle, and cotyledon, was induced using Murashige and Skoog (MS) medium supplemented with different plant growth regulators. The combination of benzyladenine at 1 mg L⁻¹ and 4-dichlorophenoxy acetic acid at 3 mg L⁻¹ was optimal for biomass production, yielding 215.88 ± 0.31 mg, with growth per gram at 8.32 ± 0.32 and a growth rate of 13.62 ± 0.25 mg/day on MS medium. For shoot proliferation, benzyladenine (3.5 mg L⁻¹) and naphthalene acetic acid (0.5 mg L⁻¹) combined with activated charcoal showed the highest shoot induction percentage per explant. For shoot regeneration from calluses, 6-benzylaminopurine (0.5 mg L⁻¹) and thidiazuron (2 mg L⁻¹) were most effective, producing superior shoot length, number of regenerations, and regeneration percentage. Root induction was successful with α-naphthalene acetic acid supplementation (0.5 to 1.5 mg L⁻¹) in MS medium, resulting in the highest number per explant (4.08 ± 0.08), length (5.45 ± 0.15 cm), and rooting rate (87.00 ± 1.66%) of roots in plantlets. Subculturing for callus culture was performed every 28 days for up to four subcultures to prevent nutrient depletion and toxic metabolite accumulation, ensuring tissue health and viability. Continuous subculturing of callus on MS medium maintained healthy <i>P. hexandrum</i> germplasm in vitro. Overall, this micropropagation protocol provides a rapid system for conserving <i>P. hexandrum</i> germplasm.