Somatic Embryogenesis and Plant Regeneration in Wedelia calendulacea Less. an Endangered Medicinal Plant

In this work, plant regeneration via somatic embryogenesis was achieved from leaf and internode derived callus of Wedelia calendulacea, an endangered medicinal plant. Primary callus was induced by culturing leaf disc and internode explant on Murashige and Skoog medium supplemented with 2.0 mg L-1 of 2,4-D under light condition. Transfer of embryogenic callus on a reduced concentration of 2,4-D facilitated somatic embryo development while calluses remained unorganized at the same 2,4-D level. A histological analysis confirmed somatic embryo by revealing the presence of a closed vascular system in the developing embryos and lack of a vascular connection with surrounding callus tissues. Somatic embryos germinated into plantlets upon transfer on MS medium containing 1.0 mg L-1 BAP plus 0.5 mg L-1 GA3. Plantlets were acclimatized successfully and survived under soil condition. This is the first on somatic embryogenesis of W. calendulacea. This result could facilitate genetic transformation of this important medicinal plant.