We report an efficient somatic embryogenesis and plant regeneration system using leaf cultures of Citrullus colocynthis (L.) and assessed the effect of plant growth regulators on the regeneration process. Initially leaf explants were cultured on Murashige and Skoog medium supplemented with different concentrations of auxins viz., 2,4-dichlorophenoxyacetic acid, 1-naphthaleneacetic acid, gibberellic acid alone and along with combination of 6-benzylaminopurine. The different forms of calli such as compact, white friable, creamy friable, brownish nodular, green globular and green calli were induced from the leaf explants on MS medium containing different concentrations of auxins and gibberellins. Subsequently initial callus was subcultured at 1.5 mg L -1 BAP ? 1.0 mg L -1 2,4-D which resulted in 25 % somatic embryos from 85 % nodular embryogenic nodular callus that is highest percentage. Similarly the lowest percentage of somatic embryos was recorded at 2.5 mg L -1 BAP ? 0.5 mg L -1 NAA from 55 % embryogenic globular callus i.e., 16 %. High frequency of embryo development takes place at intermittent light when compared with continuous light in the individual subcultures. The cotyledonary embryos were developed into complete platelets on MS medium. In vitro regenerated plantlets were washed to remove the traces of agar and then transferred to sterile vermiculite and sand (2:1) containing pot.

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In the present study in vitro mutagenesis was used to study the effect of gamma irradiation and EMS on callus induction, morphogenesis and production of multiple shoots from different explants of Citrullus colocynthis (L.) Schrad. Gamma radiations (5 kR to 20 kR) and certain chemicals have been effected on plant growth developments and changes of biochemical metabolisms in plants. Murashige and Skoog (MS) medium containing with auxins such as NAA, IAA, 2,4-D (0.5~2.0 mg/l), cytokinines BAP, kn TDZ, (0.5~2.5 mg/l), L-Glutamic acid (1~2 mg/l) and Coconut milk (10~20%). After 5 weeks on induction media, explants and callus (EC) were exposed to 5 kR, 10 kR, 15 kR and 20kR, of gamma radiation and treated with 1, 2, 3, 4 and 5 mM ethyl methane sulphonate (EMS) for 30 min. The highest percentage of callusing was observed (70%) stem irradiated with 5 kR and significantly decrease in fresh and dry weight of callus in the below 4 kR doses and above 20 kR doses, there was a progressive decrease in the fresh weight and dry weights when compared to control callus. Maximum percentage of plantlet regeneration (59%) was induced from callus exposed to 15 kR gamma irradiation on MS media fortified with 2.0 mg/l 2,4-D + 2.0 mg/l BAP + 2.0 mg/l L-glutamic acid. Increase in gamma irradiation dose above 15 kR and 5 mM EMS reduced regeneration capacity of callus. Doses higher than 20 kR and 7 mM EMS was lethal to micropropagated plants of Citurullus colocynthis.

An efficient procedure has been developed for induction of adventitious rooting and proliferation from different explants of Citrullus colocynthis. Leaf, stem, cotyledon and hypocotyledon explants cultured on different concentration of auxins and cytokinins, were supplemented on MS medium to test their ability to induce rhizogenesis. Murashige and Skoog (MS) medium fortified with 2,4-dichlorophenoxyacetic (2,4-D), indoleacetic acid (IAA), Indole-Butyric Acid (IBA) and Naphthalene Acetic Acid (NAA). Each at the concentrations of 0, 0.5, 1.0, 1.5, 2.0 and 2.5 mg LG 1 were evaluated for their effects on adventitious root induction in the present study. High concentration of IAA (2.0 mg LG 1) and low concentration of IBA (1.5 mg LG 1) is best for induction of rhizogenesis. High concentration of IBA favored formation of malformed and thick roots. The NAA in combination with IBA is most potential in inducing high percentage of rooting (50%) and IAA in combination with IBA induced maximum rooting 62% with highest number of roots per shoot (3.80±0.2) and root length (3.8±0.1 cm) were obtained from leaf, cotyledon and stem than hypocotyls. Results revealed that, the best rooting ability was observed from in stem explants cultured on MS medium supplemented with 2.0 mg LG 1 IAA and 1.5 mg LG 1 IBA, multiple roots fibrous were produced from cotyledon explants on MS fortified with 2.0 mg LG 1 2,4-d and multiple roots cluster produced from leaf explants 1.5 mg LG 1 IBA and 2.0 mg LG 1 IAA. A distinct feature of this study is the adventitious rooting and proliferations from different explants of Citrullus colocynthis which has not been reported previously.