In vitro asymbiotic seed germination and micropropagation of Dendrobium heyneanum Lindl. - an endemic orchid of Western Ghats, India

Dendrobium heyneanum Lindl. or Heyne's Dendrobium is an endemic epiphytic orchid of Western Ghats, with a height of approximately 3 - 4 inches. The present study aimed to establish a conservation strategy using in vitro regeneration methods for this endangered taxon. Mature pods of the D. heyneanum were collected from the field, and aseptically inoculated on various nutrient media. Asymbiotic seed germination was most successful on half-strength macro-MS media, yielding an 86.70% germination rate within 12 days. Different morphogenic stages (I-VI) were observed, with 20.84% of seeds producing young seedlings with roots on half-strength macro-MS media. The micropropagation protocol of D. heyneanum was established by using the protocorms (Stage IV) from the asymbiotic germinated seeds, with the highest frequency (90.20%) observed in 1.0 mg/L Kinetin (KN). In vitro flower buds were observed at 0.5 mg/L and 1.0 mg/L 6-Benzyl amino purine (BAP) and callus induction at 2.0 mg/L of BAP. The synergistic effect of KN combined with auxins - alpha- Naphthaleneacetic acid (NAA), Indole- 3- acetic acid (IAA), and Indole- 3- butyric acid (IBA) plantlets were assessed, with KN + IAA (1.0 mg/L) inducing pseudobulb elongation (0.92 cm) and rooting (0.74 cm). The plantlets were subsequently acclimatized and hardened on pots containing cocopeat and brick pieces resulting in a survival rate of 52.73%. This study presents a comprehensive protocol for in vitro propagation of Dendrobium heyneanum Lindl., offering a viable method for ex-situ conservation efforts.