Callus formation and plant regeneration from callus through somatic embryo structures in Cymbidium orchid

Embryogenic calli were induced from longitudinally bisected segments of protocorm-like bodies (PLBs) of Cymbidium Twilight Moon ‘Day Light’, a hybrid orchid, on modified Vacin and Went medium [Bot. Gaz. 110 (1949) 605] supplemented with 1-naphthaleneacetic acid (NAA) or 2,4-dichlorophenoxyacetic acid (2,4-D) alone or in combination with N-phenyl-N′-1,2,3-thiadiazol-5-yl urea (TDZ) within 1 month. The medium containing the combination of 0.1 mg l−1 NAA and 0.01 mg l−1 TDZ was optimal for callus formation. Calli proliferated very well when being subcultured every 4 weeks on the same medium. The PLB formation from callus was achieved when callus was transferred to the medium without plant growth regulators. Histological observation proved the somatic embryo structure formation. Callus-derived PLBs converted into normal plants with well-developed shoots and roots on the medium without plant growth regulators after about 4 months, which were acclimatized in the greenhouse with 100% survival rate. Among 103 twenty-month-old regenerated plants, no morphological variations were observed. © 2004 Elsevier Ireland Ltd. All rights reserved.