Different modes of plant regeneration and factors affecting in vitro bulblet production in Ornithogalum virens

Efficient procedures are outlined for plant regeneration through direct shoot bud formation and indirect organogenesis through callus formation in Ornithogalum virens Lindl using bulb scale as explant. Murashige and Skoog’s (MS) medium containing 1 mg/L (5.4mM) NAA and 2 mg/L (4.4mM) BA was most effective in direct induction of shoot buds from explant. Callus cultures were raised from the bulb scale segment on MS medium supplemented with 2 mg/L (9.0mM) 2,4-D. Shoot regeneration from callus was optimum on the medium containing 2 mg/L (10.7mM) NAA and 0.5 mg/L (2.2mM) BA. Shoots developed roots on MS basal medium devoid of growth regulators. Regenerated plants grew profusely in MS liquid medium and were successfully transferred to pots. Bulblets were induced at the base of the regenerants upon transfer to MS basal medium supplemented with enhanced concentrations of sucrose (45 to 90 g/L). Direct induction of bulblets also occurred on the bulb scale grown on the MS media supplemented with 1 mg/L (5.4mM) NAA, 2 mg/L (8.9mM) BA and 60 g/L sucrose. Size of bulblets could be increased by decreasing the salt strength of MS basal medium to half. The effect of in vitro induced bulblet size on the ex vitro survival rate was also reported. Bulblets produced in vitro could be transplanted directly to potted soil. Chromosome analysis of direct explant-derived plants, callus-derived regenerates, and plants sprouted from in vitro-induced bulblets revealed only diploid cells with normal karyotypes comprising 2n = 6 chromosomes. List of abbreviations: NAA, a-naphthalene acetic acid; BA, 6 benzyladenine; 2,4-D, 2,4 dichlorophenoxyacetic acid.