Efficient plant regeneration protocol through callus for Saussurea obvallata (DC.) Edgew. (Asteraceae):: effect of explant type, age and plant growth regulators

A callus induction and in vitro plantlet regeneration system for the endangered state flower of Uttaranchal ( Saussurea obvallata) was optimized by studying the influence of explant type ( root, hypocotyl, cotyledon and leaf), age and different concentrations of plant growth regulators. Explants from 10 to 15-day-old seedlings showed maximum callus induction. Callus formation and shoot differentiation was initiated on Murashige-Skoog ( MS) medium containing 6-benzyladenine ( BA) and alpha-naphthalene acetic acid (NAA) in all explant types. The best results were obtained using leaf explants: 100% callusing was achieved in MS medium supplemented with 2.5 mu M BA and 1.0 mu M NAA, and 100% differentiation along with a multiplication rate of 12 shoots per explant with a combination of 5.0 mu M BA and 1.0 mu M NAA. However, the results reflected the existence of high inter-explant variability in response to growth regulators. In vitro rooting of shoots was achieved at an efficiency of 100% in one-half strength MS medium supplemented with 2.5 mu M indole-3-butyric acid. Application of this protocol has potential for mass multiplication of the target species in a limited time period.