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Organogenesis from Leaf-derived Calli of S. potatorum L. f.: A Vulnerable Medicinal Tree Species

An efficient protocol for in vitro regeneration of Strychnos potatorum L. f. through indirect organogenesis was developed using mature leaf disc explants. The explants were selected from twenty years old tree. Cultured on Murashige and Skoog’s medium supplemented with 2,4-dichloro phenoxy acetic acid (2,4-D) was used for the induction of organogenic calli. A pale yellow coloured friable callus developed at 2 mg/L-1 2,4-D where showed higher morphogenic potential. Further de-novo shoots formation and multiplication in optimal concentrations of cytokinins with different combinations of auxins.  An average mean shoots number (14.2±0.42) and shoots height (3.5±0.27cm) was obtained from piece of calli in 6-benzylaminopurine (BAP) 1 mg/L-1 with 0.5 mg/L-1 α-naphthalene acetic acid (NAA). BAP in combinations with NAA was found to be superior to shoot development than other combination used. The well developed shoots were transferred to root induction medium for effective rooting. The rooting medium consisted of in half-strength MS medium augmented with 0.5 mg/L-1 NAA was used. The maximal mean number of roots per shoots 6.5±0.53 was recorded in 4 weeks. The rooted plantlets were removed from the culture tubes, gently washed with sterile double distilled water to remove agar adhering on the plant surface. The regenerated plants were transferred to plastic cups filled with a potting mixture containing sterile sand and soilrite (1:1 ratio) and allowed to grow in the greenhouse. The slowly acclimatized plants were further transferred to substrate containing red soil and farmyard manure (1:1) for effective hardening. 75% survival rate was recorded. This protocol can be useful for the ex-situ conservation and rehabilitation of this vulnerable medicinal tree S. potatorum. 
Keywords: Indirect organogenesis, friable callus, shoot development, 6-benzylaminopurine, α-naphthalene acetic acid