Direct Somatic Embryogenesis and Regeneration of an Indonesian orchid Phalaenopsis amabilis (L.) Blume under a Variety of Plant Growth Regulators, Light Regime, and Organic Substances

Phalaenopsis amabilis is an Indonesian native orchid often used as parent to produce various orchid hybrids. However, this natural orchid is increasingly difficult to find growing naturally in the forest due to over-harvesting and destruction of its natural habitat. The objectives of this study were to investigate the effect of plant growth regulators (PGRs), light regime, and organic substances on the induction and regeneration of somatic embryos (SEs) of P. amabilis orchid. Root, stem, leaf, and protocorm explants were cultured on New Phalaenopsis (NP) medium supplemented with thidiazuron (TDZ) (0.0, 1.0, 2.0, 3.0 mg L^-1) in combination with a-napthalene acetic acid (NAA), 2,4-dichlorophenoxyacetic acid (2,4-D), and indole acetic acid (IAA) with concentrations of 1.0, 2.0, and 3.0 mg L^-1. Light and dark conditions were tested for their effectiveness to induce the formation of SEs, and the resulting SEs were cultured on NP medium supplemented with various organic substances (banana, bean sprout, tomato, and potato extracts) with concentrations of 50, 100, 150, 200, and 250 g L^-1. Results showed that the highest number of SEs (36.45 ±0.26 embryos) was found in stem explants cultured in NP medium supplemented with 3.0 mg L^-1 TDZ and 1 mg L^-1 NAA. When explants were cultured in dark conditions, the number of SEs significantly increased with the highest number of SEs achieved in stem explants culture in 3.0 mg L^-1 TDZ and 1.0 mg L^-1 NAA. NP medium supplemented with 150 g L^-1 tomato extract was the most effective medium for growth of SEs-derived plants. Seedlings of this treatment produced an average of 4.20 ±0.17 leaves and 3.20 ±0.11 roots after 12 weeks of culture. In conclusion, SEs can be produced effectively from stem explants with a combination of 3.0 mg L^-1 TDZ and 1.0 mg L^-1 NAA, one month early in dark conditions, and regenerated on NP medium with addition of tomato extract. © 2021 Elsevier B.V., All rights reserved.