In vitro Micropropagation of Citrullus colocynthis (L.) Schrad: an endangered medicinal plant

Background: The experiment describes the establishment of in vitro conditions for seed germination, micropropagation, callogenesis, organogenesis and acclimatization of Citrullus colocynthis (L.) Schrad, of family Cucurbitaceae. Methods: In vitro grown seedlings from decontaminated seeds were micropropagated in basal MS medium at 23 +/- 2 degrees C temperature and light intensity of 3000 Lux for 16 hours in culture room. In vitro grown nodal explants were supplemented with BAP (6-Benzylaminopurine) and NAA (Naphthalene acetic acid) with basal MS (Murashige and Skoog) medium to induce multiple shoots. Indole butyric acid (IBA; 0.1 to 2.0 mg/L) was supplemented to MS medium to develop roots of micropropagated shoots. Internodes and leaves of micropropagated shoots used to induce callus in MS medium enriched with varying concentration of 2, 4-dichlorophenoxyacetic acid (2, 4 D; 0 to 2.0mg/L) and kinetin (KIN; 0 to 1.0mg/L). Shoot initiation from callus was tested by adding 2, 4-D (0.1 to 2.0 mg/L) and BAP (1.0 to 1.5 mg/L) in basal MS medium. Conditions were carefully monitored during the experiment. After hardening, the micropropagated plantlets were placed in open filed environment in pots filled with sand and peat moss (3:1). Result: Surface sterilized seeds of Citrullus colocynthis (L.) showed 100% germination in regulator free medium. Significantly mature shoots (75%) from nodal explant recorded in BAP (2.0 mg/L) and NAA (1.0 mg/L) augmented MS medium. Highest number (90%) of roots per shoot explant were observed in IBA (2.0 mg/L). Leaf explants showed better response to form callus with a combination of 2, 4-D (1.0 mg/L) and KIN (1.0 mg/L) and further rise in 2, 4-D concentration caused a sharp decrease in callus formation. Shoot induction from callus cultures observed in MS medium containing 2, 4-D (2.0 mg/L) and BAP (1.5 mg/L), producing an average of 10 shoots per culture. Plants were effectively transplanted in open environment with survival rate of 85%. Conclusion: Results indicate the successful establishment of the growth room conditions for in vitro micropropagation of the endangered medicinal plant, Citrullus colocynthis.