A protocol for regenerating and subsequent
in vitro flowering of an economical important and endangered
medicinal orchid, Dendrobium huoshanense, was
established mainly via indirect protocorm-like body (PLB)
formation. A four-step method was developed to induce
successful plant regeneration on 1/2 MS medium supplemented
with suitable plant growth regulators (PGRs). Step
1 (callus induction): the root tip explants (1 cm long) were
cultured at 1 mg l-1 2,4-D ? 1 mg l-1 TDZ for 3 months.
Step 2 (callus proliferation): the calli were subcultured with
a 1-month interval at 1 mg l-1 2,4-D ? 1 mg l-1 TDZ.
Step 3 (PLB induction): the calli were cultured at 2 mg l-1
NAA ? 1 mg l-1 BA for 2 months. Step 4 (plantlet conversion):
the 2-month-old PLBs were cultured at
0.1 mg l-1 IBA for 4 months. It took at least 6 months to
produce well-rooted regenerated plantlets with an average
of 3.2 roots and 3.6 leaves from the initial callus. The
6-month-old rooted plantlets were transferred onto PGRfree
1/2 MS medium for 6 months, and then potted with
Sphagnum moss for acclimatization. After 2 month of
culture, the survival rate was 100 %. The in vitro flowers
were obtained on the 8-month-old plantlets at 1 mg l-1
IBA, 5 mg l-1 IBA and 0.1 mg l-1 NAA, but the flowers
showed a lack of the gynandrium. The abnormity was
overcome by the aid of 5 mg l-1 TDZ, and subsequently,
the capsules formed without artificial pollination. This
protocol provides the basis for further investigation on cell
suspension, micropropagation, in vitro flowering and
breeding programs in Dendrobium huoshanense.