Somatic embryogenesis in Oncidium

In vitro plant regeneration of Oncidium spp. was established through direct and indirect somatic embryogenesis. 1) Leaf segments taken from in vitro grown plantlets could directly form somatic embryos within one month, when cultured on a hormone-free 1/2-strengh modified MS (Murashige and Skoog, 1962) medium in darkness. In light, these embryos germinated into somatic protocorms on the same medium. Embryo-derived protocorms developed into healthy plantlets with 100% survival rate when acclimated in a greenhouse. 2) Embryogenic calli were induced from flower stalk internodes, leaf, root and stem explants on a 1/2-strengh modified MS medium (basal medium) supplemented with 3 mg/l 2,4-D and 1 mg/l TDZ in darkness. Somatic embryos formed from the calli on a hormone-free basal medium. Explant type strongly affected the amount of embryogenesis, and root callus has the highest competence to form embryos. Normal plantlets were obtained from the calliderived embryos on a basal medium supplemented with 0.5 mg/l NAA. The plantlets grew well when transferred to a greenhouse. The protocols for plant formation of Oncidium through somatic embryogenesis could be useful for the mass propagation and transformation of selected elite lines.