Callus formation and organogenesis of tomato (Lycopersicon esculentum Mill, C.V. Omdurman) induced by thidiazuron
AbstractIn vitro culture response was assessed in tomato (Lycopersicon esculentum Mill. c. v. Omdurman) for optimum callus induction and plantlet regeneration. Callus induction was achieved within seven to ten days directly on the cut surfaces of both hypocotyls and cotyledon explants cultured on Murashige and Skoog (MS) basal medium supplemented with -naphthalene acetic acid (NAA), 2,4-dichlorophenoxyacetic acid (2,4-D), Thidiazuron (TDZ) and benzyl adenine (BA) alone or in different
combinations, but not in hormone free-medium. The highest callusing index (5.3) was obtained on hypocotyls explants cultured on MS medium supplemented with NAA at 0.5 mg/l followed by an index of 5.2 obtained from the same explant by using 0.1 mg/l NAA in combination with BAP at 0.5 mg/l. However, for the cotyledon explants, the highest callusing index (4.7) was obtained on MS medium supplemented with NAA at either 2.0 or 3.0 mg/l. After 8 weeks of culture, organogenesis was observed only on the explants cultured on medium containing different concentrations of TDZ alone or in combination with BAP. The best shoot formation (93%) was obtained for cotyledon explant callus induced on MS medium containing TDZ in combination with BAP both at 0.5 mg/l. The highest number
(6) of shoot per explant was obtained when cotyledon explant callus was sub cultured on MS medium supplemented with 3.0 mg/l TDZ. Plain half strength of MS was found to be the best rooting medium, however, addition of IAA at 1.0 mg/l and IBA at 2.0 mg/l were found essential to induce highest number of roots (22.1 ± 0.9) and longer roots (11.0 ± 0.3 cm), respectively. This protocol would be useful to create somaclonal variation and utilize transgenic approaches for varietal improvement of tomato.