Isolation, callus formation and plantlet regeneration from mesophyll protoplasts of Tylophora indica (Burm. f.) Merrill: an important medicinal plant
2009
Thomas, T Dennis
Protoplast culture and plant regeneration of an important medicinal plant Tylophora indica were achieved through callus regeneration. Protoplasts were isolated from leaf mesophyll cells and cultured at a density of 5 × 10⁵ protoplasts per gram fresh weight, which is required for the highest frequency of protoplast division (33.7%) and plating efficiency (9.3%). The first division was observed 2 d after plating and the second division after 4 d. Culture medium consists of Murashige and Skoog (MS) liquid medium with 4 μM 2,4-D, 0.4 M mannitol and 3% (w/v) sucrose with pH adjusted to 5.8. After 45 d of culture at 25°C in the dark, protoplasts formed colonies consisting of about 100 cells. The protoplast-derived microcalli were visible to the naked eye within 60 d of culture and reached a size of 0.2-0.4 mm in diameter after 90 d. Calli of 0.2-0.4-mm size were transferred to MS medium supplemented with 2,4-D (4 µM), 3% (w/v) sucrose and 0.8% (w/v) agar, formed friable organogenic calli (7-8 mm size) after 8 wk under incubation in normal light period supplemented with 200 µmol m⁻² S⁻¹ of day light fluorescent illumination. The calli were transferred to MS medium supplemented with thidiazuron (TDZ) (1-7 μM) and naphthalene acetic acid (NAA) (0.2-0.4 μM) for regeneration. The calli developed shoot buds after 3-4 wk, and the frequencies of calli-forming shoots varied from 5% to 44%. Optimum shoot regeneration occurred on MS medium supplemented with 5 μM TDZ and 0.4 μM NAA. On this medium, 44% cultures responded with an average number of 12 shoots per callus. Whole plants were recovered following rooting of shoots in 1/2 MS medium supplemented with 3 μM indole 3-butyric acid.
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