Development of Cost Effective In Vitro Regeneration Protocol of Malaxis acuminata D. Don a Therapeutically Important Orchid Using Pseudobulbs as Explant Source

Abstract

This communication reports the in vitro culture of pseudobulb segments of Malaxis acuminata D. Don. and screening of some low cost substrata as alternative to agar. About 8-10 week old pseudobulb from the in vitro sourced plants were harvested and longitudinally cut into two halves and cultured. Within 5-6 week of culture, about 98 percent of pseudobulb segments responded positively and formed as many as 11 shoot buds per explants on MS medium enriched with sucrose (3%, w/v), casein hydrolysate (100 mg L-1) and ?-naphthalene acetic acid (NAA) + N6 benzyl adenine (BA) (6 µM each in combination). Incorporation of lower activated charcoal (< 0.3%) in the initiation medium did not promote shoot bud formation but a concentration of 0.3% (w/v) promoted healthy root formation and pigmentation of the plantlets. The shoot buds were converted into rooted plantlets and distinct pseudobulbs on medium containing sucrose (3%), and NAA and BA (3 µM each in combination) where as many as 18 shoot buds, protocorm-like bodies (PLBs) were developed per subculture. Among the three alternative substrata incorporated in the regeneration medium, regenerative response on ‘foam disk’ as substratum was competitive with agar gelled medium while regeneration on coconut coir and forest litter were underperformed. Production cost could be substantially reduced (about a fourth) by using foam as agar alternative. The transplants were maintained in a poly-shade (~75% shade) for about 8 week before transferring to the natural habitat where about 75% of the transplants survived.