DISCUSSION
The specific combination of
auxin and cytokinin in culture media is
one of the most important factors for in
vitro regeneration of orchids. In this
study, we found that the most suitable
plant growth regulators for proliferation
and regeneration of V. lilacina were NAA
and BAP. Treatment with selective agents
is needed to avoid development of
undesirable numbers of escaped plants.
In this experiment, the selection agent
was hygromycin, an aminoglycoside
antibiotic that causes death to plant cells
by inhibiting transcription and translation
(Datta et al., 1999). We found that the
effective concentration of hygromycin for selection of the transformants was
9 mg/l.
Co-cultivation period is another
factor which affects the ef¿ ciency of
Agrobacterium-mediated transformation.
The optimal co-cultivation time for
V. lilacina was shown to be 30 minutes.
These transformed protocorms gave a
high intensity of blue staining that
indicated high GUS expression. In this
study, the transformation percentage of
V. lilacina was 54. DNA integration was
con¿ rmed by PCR ampli¿ cation of 195
bp and 180 bp for the 35S promoter and
NOS terminator, respectively. The
present research has shown the same
results as those reported for Dendrobium