Simplified Regeneration Protocol for Cycas revoluta Thunb. Mature Zygotic Embryos

Abstract

Mature zygotic embryos of Cycas revoluta Thunb. were used as explants to investigate direct and indirect organogenesis. Explants were incubated on half-strength Murashige and Skoog (½ MS) basal medium supplemented with various plant growth regulators, singly or in combination (all at 0.5 mg l^-1): 6-benzyladenine (BA), kinetin (Kin), 2,4-dichlorophenoxyacetic acid (2,4-D), Kin×2,4-D, BA×Kin and BA×2,4-D. Cultures were placed at a low light intensity (4 μmol m^-2 s^-1 PPFD). Adventitious shoot regeneration was observed in the presence of 0.5 mg l^-1BA after 35 days. The highest number of direct and indirect shoots per zygotic embryo was 3.67 and 29.67, respectively. Roots were induced on indirect shoots by continuous culture on rooting medium (½ MS,þ 0.1 mg l^-1 1-naphthaleneacetic acid) and hardened successfully in perlite. Each rooted plantlet with pinnate leaves and a primary tap root was individually isolated and acclimatized 185 days after the beginning of culture, with a 10% success rate.