In vitro regeneration of plantlets from direct and indirect organogenesis from axenic stem nodal explant culture of a rare orchid Dendrobium jerdonianum Wight.

Abstract

Direct and indirect in vitro plant regeneration protocol for Dendrobium jerdonianum has been established. Juvenile stem nodal segments were used as explants to initiate the axillary buds/callus. Node explants derived from 7-8 months old in vitro grown seedlings cultured on half strength Murashige & Skoog (MS) medium (½ MS) and supplemented with various plant growth regulators (PGRs) viz., α-naphthalene acetic acid (NAA), 6-benzyl amino purine (BAP), kinetin (KN) and thidiazuron (TDZ) either individually or in combinations produced axillary buds/callus. The highest average number of shoots per explants were achieved in ½ MS medium supplemented with BAP (3.23 μM) induced the optimum response of 76.3% of direct shoots and forming an average number of 4.9 shoots per explant. Synergistic effects of combinations of various PGRs on direct shoot induction were evaluated. The combinations of NAA (0.5 μM) + BAP (1.62 μM) and NAA (0.5 μM) + KN (0.47 μM) induced 70.2 and 64.3% of direct shoots, respectively. On sub-culturing the shoots in the medium containing NAA (2.69 μM) allows for further growth and rooting, developed into plantlets after 14 weeks of culture. The stem nodal explants cultured on ½ MS medium supplemented with NAA (0.5 μM), TDZ (4.54 μM) and combination of NAA (0.5 μM) + TDZ (2.27 μM) induced the optimum amount of organogenic callus of 39.6, 49.3 and 72.6%, respectively. On sub-culturing the organogenic callus derived from the explants developed the protocorm like bodies (PLBs) in the same media. These PLBs differentiated into plantlets after 18-21 weeks of culture. Almost 90% of the plantlets were successfully acclimatized in the potting mixture and established ex vitro.