Materials and Methods
Plant materials
In experiment 1, the PLBs of Dendrobium Sonia
‘Earsakul’ derived from in vitro axillary bud culture
was used as initial explants for somatic embryogenic
formation. In experiment 2, the age of young
plantlets of Dendrobium Sonia ‘Earsakul’ at 6
months of culture (leaf length about 1.0 cm measured
from the axillary bud) was cultured in vitro to induce
PLBs formation and regeneration. Two weeks before
the experiments, the PLBs and young plantlet were
cultured on Vacin and Went (1949) (VW) solid
medium, in which pH was adjusted to 5.5 and with
no PRGs added.
Direct somatic embryogenesis
Somatic embryogenesis from PLBs
The PLBs at the stage of shoot apical emergent
were transferred onto solidified half-strength
Murashige and Skoog (MS) medium (Murashige
and Skoog, 1962) containing 30 g/L sucrose and
different concentrations of thidiazuron (TDZ) either
at 0.1, 0.3 and 1.0 mg/L alone or in combinations
with 0.1 mg/L naphthaleneacetic acid (NAA) or 1.0
mg/L 2,4-dichlorophenoxyacetic acid (2,4-D). PLBs
were cultured on the media in Petri’s dishes with 12
replicates per treatment.
Somatic embryogenesis from leaf segments
A half-strength MS medium supplemented with
TDZ either at 1.0 and 3.0 mg/L alone or in
combination with 0.1 mg/L NAA was used to culture
leaf segments to induce embryogenic callus. A
young leaf derived from young plantlet was divided
into 2 segments, apical and basal segment (about
0.5 cm long) and cultured on the medium in two
orientations, either dorsal or ventral side placing on
a medium. All explants were cultured in 120-mL
bottles containing 30 mL of culture medium with
14 replicates per treatments.