Seed storage and asymbiotic germination of Hadrolaelia grandis (Orchidaceae)

• Protocol for in vitro propagation and conservation of Hadrolaelia grandis.
• A temperature of – 80 °C is recommended for the storage of H. grandis seeds.
• The WPM medium exhibited the best germination and seedling development of H. grandis.
• Activated charcoal improves the vigor and growth of H. grandis seedlings.

Hadrolaelia grandis is an endangered species of orchid that is experiencing population declines due to habitat destruction and collection for ornamental purposes. Seed storage, in vitro germination and development of seedlings for propagation were investigated. Tetrazolium test (TZ) and asymbiotic germination were used to evaluate seeds stored at − 20 °C and − 80 °C for 24, 30, and 36 months. Seeds were germinated on Woody Plant Medium (WPM), Murashige & Skoog (MS), Vacin & Went (VW) and Knudson C (KC) media. The temperature of − 80 °C was the most effective for seed storage since the percentage of viable seeds (81.86%), as determined by TZ, was higher than those stored at − 20 °C (64.24%) for 36 months. WPM proved to be the most effective medium for seed germination and seedling development (94.71%, and a germination speed index of 25.33) after 36 months of storage at − 80 °C. Protocorm elongation and root development were achieved on WPM medium containing activated charcoal (1 g L− 1), and after 16 weeks seedlings were successfully acclimatized after 12 weeks (91.07% survival rate) using vermiculite as a substrate.