An Efficient Micropropagation System for Morinda officinalis How. (Rubiaceae), an Endangered Medicinal Plant

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The present work developed an efficient plant regeneration and propagation system via direct organogenesis for Morinda officinalis How., a valuable endangered medicinal plant. The effects of explant types on shoot induction, plant growth regulators on shoot proliferationand elongation and the subsequent rooting ability of shoots were examined. Among the various types of explant, direct shoot proliferationwas successfully achieved from shoot tips and nodal stem segments with around 95% of the explants producing approximately 5 shoots per explant after 8 weeks of culture on optimal medium. On the other hand, leaf and internodal explants did not produce any shoots. The most effective cytokinin on shoot proliferation was 6-benzyladenine. When the concentration of 6-benzyladenine was at 1.0-2.0 mg L-1, a high mean shoot number (about 5 shoots per explant) was achieved. Shoot elongation was obtained satisfactorily by transferring the shoots to Murashige and Skoog basal media containing 2.0-3.0 mg L-1 gibberellic acid-3 within 2 weeks. Rooting was 100% on half-strength Murashige and Skoog medium containing 0.2 mg L-1 indole-3-butyric acid after 3 weeks of culture. The plantlets were acclimatized in the greenhouse and subsequently transferred to the field with 90% survival rate.