Improvement of In Vitro Seed Germination and Shoot Development of the Indonesian Endangered Orchid, Dendrobium...

Dendrobium lineale Rolfe is an important orchid species used as a parent in breeding. Currently, this orchid is classified as an endangered species and is listed in Appendix II according to CITES. This study aimed to investigate the effects of sucrose and coconut water (CW) on the asymbiotic seed germination and shoot development of this endangered Indonesian orchid. In vitro orchid seed culture aids in conservation and reintroduction. Three-month-old hand-pollinated seeds were sown on Vacin and Went (VW) solid medium supplemented with several concentrations of sucrose (10, 20, and 30 g/L) or without sucrose (controls). Seed germination and protocorm development were investigated 1, 2, and 3 months after sowing. To analyze the role of CW in subsequent shoot development and root formation, shoots with an approximately 1-cm length and comprising 1-2 leaves obtained following seed germination were cultured on VW medium supplemented with several concentrations of CW (5%, 10%, 15%, and 20%) and without CW (control) treatment. After 4 months of culture, the number of roots, the number of leaves, and dry weight of the plantlets were recorded. VW medium containing 20 g/L sucrose effectively enhanced seed germination (89%) and shoot formation with one or more leaves (stage 5) (46%). Supplementation with 20% CW in VW medium was suitable for shoot development, resulting in well-developed roots and leaves and improved fresh weight of plantlets compared with those in the other treatments. Moreover, 87% of the acclimatized plantlets survived. This protocol is an efficient method for the in vitro mass production and conservation of this endangered epiphytic orchid using asymbiotic seed culture.