In Vitro Regeneration and Agrobacterium Transformation of Echinacea purpurea Leaf Explants*

Echinacea has gained considerable attention because of its increasing economic value and use as a medicinal plant. The genus Echinacea, Asteraceae, is represented by eleven taxa found in the United States and in south central Canada. Echinacea purpurea is the most widespread species (McGregor 1968) and the most widely cultivated medicinal species of the genus (McKeown 1999). Echinacea species have long been recognized as important medicinal plants and were used by Native Americans for the treatment of many diseases, including colds, toothaches, snake bites, rabies, and wound infections (Bauer and Wagner 1991). The pharmacological activity of Echinacea extracts has been widely studied with over 350 published studies to date (Briskin 2000) together providing strong evidence for an immune modulating activity of these extracts. However, little scientific research has been directed toward understanding the biosynthetic pathways of the several classes of compounds that are thought to be responsible for the biological activity of Echinacea extracts or the physiology regulating their accumulation. The transfer of foreign genes into plants has provided new ways to study regulation of development and biosynthetic processes. Agrobacterium tumefaciens mediated transformation is preferred because of its simplicity and efficiency in providing stable integration of transferred DNA into the plant genome. In vitro shoot regeneration of E. purpurea has been reported from petiole explants (Choffe et al. 2000a) and leaf tissue (Koroch et al. 2001) while root organogenesis has been obtained from hypocotyl and cotyledon explants (Choffe et al. 2000b). The objective of this work was to develop an efficient in vitro regeneration method and an Agrobacterium tumefaciens transformation method for E. purpurea leaf explants.