A protocol was developed for in vitro plantlet regeneration of Citrullus colocynthis using stem explants which was selected after screening of different seedling explants. Contamination free culture was established treating stem explants with 0.1% HgCl2 for 3 min. Optimum sucrose concentration for callus formation was 3%. The role of different growth additives like pyridoxine and thiamine HCl was assessed in enhancing callus number. The maximum number of callus induction was achieved from stem explants on MS medium enriched with 0.5 mg L-1 IAA, 2,4-D and 1 ppm of 6-BA which yielded morphogenic compact hard greenish white calli at a frequency of 80% than compared to MS medium enriched with other combination of auxin and cytokinin. Compact, hard, white/greenish white callus was formed in different amount at all concentration after 4 weeks interval. Then the callus was transferred to the shooting medium containing different concentration of auxin and cytokinin (MS medium with 1.5 mg L-1 6-BA and 0.5 mg L-1 NAA) showed better shooting. The regenerated shoots were further elongated on same medium. In vitro shoots were excised from shoot clumps and transferred to rooting medium containing 6-benzyl adenine (6-BA, 3.0 mg L-1) with 0.2% activated charcoal. The rooted plants were hardened in polycups containing sterile soil and vermiculite and finally well established in the field.
K. Satyavani, T. Ramanathan and S. Gurudeeban, 2011. Effect of Plant Growth Regulators on Callus Induction and Plantlet Regeneration of Bitter Apple (Citrullus colocynthis) from Stem Explant. Asian Journal of Biotechnology, 3: 246-253.