In Vitro Propagation of Gastrochilus matsuran (Makino) Schltr., an Endangered Epiphytic Orchid

Gastrochilus matsuran (Makino) Schltr. (Orchidaceae) populations are declining quickly because of overexploitation, climatic changes, and deforestation; therefore, mass-production protocols are required for this orchid. Natural propagation of this species is often hampered by meager seed germination and slow growth. Thus, our aim was to establish an effective protocol for the in vitro propagation of G. matsuran and reduce the risk of its extinction. We investigated the impacts of culture media, coconut water (CW), and plant hormones (gibberellic acid (GA(3)), indole-3-acetic acid (IAA), indole-3-butyric acid (IBA), α-naphthaleneacetic acid (NAA), and thidiazuron (TDZ)) on asymbiotic germination, multiplication and conversion of protocorms, and plantlet development. Maximal seed germination (93.3%) was achieved on ½ MS medium without vitamins plus 5% CW, 1 µM NAA, and 1.5 µM GA(3). Secondary protocorm formation was best achieved on ½ MS medium without vitamins plus 2 µM TDZ. The conversion of protocorms into seedlings was maximized by supplementation with 2 µM IBA or 1 µM NAA. Acclimatized plantlets that exhibited exuberant growth on sphagnum moss were reintroduced to tree trunks in a natural habitat, with a 67% survival rate. This in vitro propagation procedure would be helpful for the mass production and conservation of this rare epiphytic orchid.