In vitro slow-growth storage of Chlorophytum borivilianum Sant. et Fernand: a critically endangered herb

A simple, in vitro multiplication and mid-term conservation system was developed for Chlorophytum borivilianum Sant. et Fernand, which is documented as a critically endangered herb on the International Union for Conservation of Nature and Natural Resources red list. In vitro shoot multiplication was achieved by culture on Murashige and Skoog medium supplemented with 2 mg L-1 6-benzyladenine and 0.2 mg L-1 naphthalene acetic acid. Continuous shoot proliferation was observed up to the seventh subculture cycle on this medium. A production cycle of 1 yr was completed when rooting and acclimatization times were included in the subculture cycle. In vitro, slow-growth storage was efficiently used for mid-term conservation of elite clones when the sucrose concentration of the medium was 120 g L-1, which enabled 100% survival from cultures stored for 4 mo without any subculture or medium addition. After 4 mo of in vitro storage, cultures transferred to the standard medium exhibited 100% regeneration, and the shoots were morphologically identical. These shoots were rooted in a medium supplemented with 2 mg L-1 indole-3-butyric acid. Rooted plantlets were transferred to the field and showed 95% survival after acclimatization. This is the first report of in vitro conservation via slow-growth storage of this important medicinal plant.