Rapid micropropagation through direct somatic embryogenesis and bulbil formation from leaf explants in Curculigo orchioides

摘要

Tuberous roots of Curculigo orchioides, an endangered medicinal plant, are widely used as tonic and aphrodisiac due to the presence of flavanone glycosides, steroids and saponins. A method has been developed for rapid multiplication of C. orchioides through somatic embryogenesis and bulbil formation directly from leaf explants. Leaf-segment (7 * 10 mm) explants transferred onto the medium supplemented with 2.2 μM BAP and 1.0 μM 2,4,5-T/1.0 μM IBA produced somatic embryos (3 per explant)/bulbils (3 per explant). Incorporation of IBA in BAP supplemented medium inhibited somatic embryogenesis but, favoured bulbils formation. Lower concentrations of KNO_3 and (NH_4)_2SO_4 in the medium favoured both, somatic embryogenesis and bulbil formation. Maximum number of somatic embryos (8 per explant) were produced on B_5 medium supplemented with 173 mgNL~(-1) as nitrate nitrogen, 85 mgNL~(-1) as ammonium nitrogen, 2.2 μM BAP and 1.0 μM 2.4.5-T. Maximum number of bulbils (10 per explant) were produced on B_5 medium supplemented with 200 mgNL~(-1) as nitrate nitrogen, 85 mgNL~(-1) as ammonium nitrogen, 2.2 μM BAP and 1.0 μM IBA. Isolated somatic embryos and bulbils were germinated on transfer to B_5 medium either devoid of plant growth regulators or containing low concentration (1.1 μM) of BAP. Plantlets developed in vitro through stem-disc culture, somatic embryogenesis and bulbil formation were successfully transferred to soil with 91%, 100% and 73% survivability, respectively. Relative vigour of in vitro raised plantlets of stem-disc origin was maximum on the basis of the number of leaves per plant, leaf area and leaf length as compared to plantlets of bulbil and embryo origin. The technique developed is highly efficient to get miniature plantlets for field transfer in 40 days, starting from an explant.