Multiple shoot formation and plant regeneration from stem nodal explants of Paphiopedilum orchids

Abstract

Stem nodal explants of Paphiopedilum philippinense hybrids (hybrid PH59 and PH60) directly formed shoots when cultured on a modified half-strength Murashige and Skoog (1962) basal medium supplemented with a combination of 2,4-dichlorophenoxyacetic acid (2,4-D: 4.52 and 45.25 μM) and 1-phenyl-3-(1,2,3-thiadiazol-5-yl)-urea (TDZ; 0.45 and 4.54 μM) for 6 mo. On hormone-free basal medium, the percentages of explants with shoots were 33.3% and 0% and the shoot numbers per explant were 1 and 0 in hybrid PH59 and hybrid PH60, respectively. In hybrid PH59, 4.52 μM 2,4-D plus 0.45μM TDZ induced a higher percentage of explants with shoots and shoot number per explant than did the hormone-free treatment. In hybrid PH60, although 4.52 μM 2,4-D and 0.45 μM TDZ promoted shoot formation, the highest shoot number was found with 4.52 μM 2,4-D alone. Plantlets, each having several roots, were obtained from regenerated shoots after transferring onto hormone-free basal medium for 3 mo. The plantlets were potted in sphagnum moss, and acclimatized well in a greenhouse.