STABILITY OF AtRKD4 GENE INTEGRATION IN THE GENOME OF DENDROBIUM PHALAENOPSIS FITZG. TRANSFORMANTS INDUCES SOMATIC EMBRYOGENESIS

Orchids are famous ornamental plants. One important orchid species is Dendrobium phalaenopsis Fitzg, a
natural orchid from Larat Island, Eastern Indonesia. This orchid became endangered due to both illegal log-
ging and deforestation. Therefore, an effective and efficient propagation method is needed. The objective of
the present study was to obtain the best explant to produce somatic embryos (SEs) from various organs. The
method is based on the number of SE and stability integration level of the AtRKD4 gene in the D. phalae-
nopsis transformant, compared to that in non-transformant plants. Activation of AtRKD4 gene expression in
transformed and non-transformed plants by using (1, 2, and 3 mg l-1
) 1-Phenyl-3-(1,2,3,-thiadiazol-5-yl) urea
(Thidiazuron; TDZ) and (10, 12, and 15 μM) Dexamethasone (DEX) and a combination of TDZ + DEX on
New Phalaenopsis (NP) medium could initiate SEs. The results showed that there are 30 SEs transformants
produced on pseudobulb higher than SE production in pseudobulb of non-transformants. Addition of 2 mg l -1
TDZ + 12 μM DEX in NP basic medium was the best treatment to produce the highest percentage (100%) of
somatic embryos from pseudobulb explants.
Key words: Dexamethasone, genetic transformation, micropropagation, pseudobulb, somatic embryo, thidi-
azuron