Asymbiotic immature seed culture of Vanda bicolor Griff., plant regeneration and formulation of an efficient new hardening technique for direct field transfer of regenerates

Abstract

Vanda bicolor Griff. is a vulnerable orchid species having immense horticultural importance. This communication reports the outcome of a successful attempt towards the formulation of immature seed culture protocol of Vanda bicolor , factors affecting effective germination, plant regeneration. This study also endeavored to formulation of a simple and effective hardening process which supports direct transfer of plantlets from the culture condition to the field. Immature seeds from green pods of 7 months old registered 88.2% germination on MS nutrient medium supplemented with 3% sucrose, 3 μM each of NAA and BA under normal culture conditions. The germinating embryos converted to protocorms and protocorm-like bodies (PLBs) on the same germination medium within 55 days of culture and subsequently converted to plantlets and supported culture proliferation and simultaneous healthy roots development on MS medium fortified with sucrose (3%), NAA and BA (3 + 6 μM respectively) and activated charcoal (0.6%) where as many as 6.2 shoots developed per subculture per PLBs and 3.3 roots per plant. A new hardening technique was developed with fortified pieces of dead wood and burnt wood. It was found that after 5–6 wk of transfer to the hardening condition, velamenous roots started adhering to the wood pieces. These plants could be transferred to polyhouse as well as in the nature directly where 98.25 and 97.75% survival rate registered respectively after 8 wk of transfer.