In vitro approaches for conservation of Asparagus racemosus Willd

Asparagus racemosus is a commercially important medicinal plant, traditionally used for combating gynecological problems in India. The majority of plants used by the pharmaceutical industry come from wild sources, endangering the natural population of the species. The plants are being overharvested, so this species faces a real danger of becoming vulnerable in its natural habitat. Ex situ conservation using in vitro tools is a possible solution to this problem. Ex situ conservation of plants involving in vitro tools has been initiated through axillary branching using nodal explants. Studies on in vitro storage under slow-growth conditions were carried out to develop an efficient protocol for conservation of A. racemosus germplasm. In vitro shoot cultures generally require a 4-wk subculture onto fresh medium when grown at 25 ± 2°C under a 16-h photoperiod. In this research, the use of mannitol or sorbitol as an osmoticum and reduction of sucrose to 1.5% (w/v) in half-strength MS medium led to maintenance of the cultures for 6 mo at 25 ± 2°C with no subculture. Surviving shoots from the slow-growth cultures could be regenerated with 100% efficiency, indicating that the subculture interval was successfully extended by this method. Temperature and medium modification both had significant effects on the growth of stored shoots, and the two factors showed significant interaction. In experiments designed to test encapsulation as a storage method, micropropagated shoot clusters encapsulated in calcium alginate beads were successfully stored up to 75 d at 25 ± 2°C under a 16-h photoperiod. Stored shoots from both storage methods were subsequently recovered and multiplied on MS medium with 3% sucrose and 1.11 μM benzylaminopurine at 25 ± 2°C. Well-developed shoots were rooted and acclimatized successfully.