In vitro regeneration of Echinacea purpurea L.: Direct somatic, embryogenesis and indirect shoot organogenesis in petiole culture

An in vitro propagation system was developed for Echinacea purpurea L. (pur ple coneflower), a medicinal plant commonly used in the treatment of colds, flu and related ailments. Echinacea seeds were found to be contaminated wi th systemic fungi and therefore an optimized minimal concentration of Plant Preservation Mixture (PPM) was incorporated in the seed germination medium to recover sterile seedlings. Regeneration was induced on petiole explants from 2-month-old sterile seedlings cultured on medium supplemented with be nzylaminopurine (BAP) or thidiazuron (TDZ) in combination with indoleacetic acid (IAA). Two distinct forms of regeneration were identified in cultured petiole explants with histological and morphological observations, viz. th e direct formation of somatic embryos on the epidermis and the de novo deve lopment of shoots from callus tissues formed in subepidermal cell layers. T he results of this study have established a micropropagation system for E. purpurea that will provide sterile plant material for further investigation s into medicinally active biochemicals and may facilitate mass production o f high-quality E. purpurea plants for the commercial market.