Multiple shoot induction and callus regeneration in Sarcostemma brevistigma Wight & Arnott, a rare medicinal plant

An efficient micropropagation protocol based on multiple shoot induction and callus regeneration has been standardized in Sarcostemma brevistigma, a rare medicinal plant. The nodal cuttings were cultured on MS medium supplemented with BA ($0.5-8{\mu}M$) or Kn ($0.5-8{\mu}M$) alone or in combination with NAA ($0.5-1.5{\mu}M$). Maximum multiple shoot induction was observed on MS medium supplemented with $4{\mu}M$ BA. On this medium, 100% cultures responded with an average number of 11.3 shoots per explant. However, the average shoot length was limited to only 0.9 cm on this medium. The addition of $1{\mu}M$ NAA along with $4{\mu}M$ BA gave rise to an average number of 10.9 shoots with an average shoot length of 1.8 cm. Luxuriantly growing callus was obtained on MS medium supplemented with BA ($5{\mu}M$) and 2,4-D ($2{\mu}M$). The callus was subcultured on MS medium supplemented with BA ($2-15{\mu}M$) or Kn ($2-15{\mu}M$) alone or in combination with NAA ($0.5-2{\mu}M$) for shoot organogenesis. Optimum callus regeneration was obtained on MS medium supplemented with $10{\mu}M$ BA and $1{\mu}M$ NAA. On this medium, 100% cultures responded with an average number of 13.4 shoots per culture. The shoots obtained via multiple shoot induction and organogenesis were rooted on half-strength MS medium supplemented with NAA ($1-7{\mu}M$) or IBA ($1-7{\mu}M$). IBA was better than NAA in terms of both the percentage of cultures that responded and the average number of roots per explant. The rooted shoots were successfully transplanted to soil with 86% success. This standardized protocol will help to conserve this rare medicinal plant.