Micropropagation of Echinacea angustifolia, E. pallida, and E. purpurea from stem and seed explants

Abstract

Micropropagation of three Echinacea species, E. angustifolia DC., E. pallida Nutt., and E. purpurea Moench., was investigated as a potential means of germplasm preservation of species faced with overcollection in the wild and rapid clonal propagation of elite individuals with unique medicinal or ornamental properties. Very high contamination rates occurred with shoot-tip explants but not with nodal segments. Contamination rates for seed explants were inversely related to the number of seedcoat layers removed, ranging from 100% contamination from intact seeds to near 0% contamination from excised embryos. Dormancy of seed explants was also eliminated when the pericarp and integument were removed. Addition of benzyladenine (BA) to the culture medium induced shoot multiplication and inhibited root formation in all three species. Shoot multiplication rates were low (1-3 shoots per culture) when seed explants were placed on a medium with BA levels low enough to avoid adventitious shoot formation (0.45 μM). Shoot count was higher on half-strength Murashige and Skoog (MS) minerals, while leaf size was greater on full-strength MS minerals. Cultures did not perform well in Woody Plant Medium. Reducing subculture frequency from 4 to 2 weeks increased shoot multiplication from 1.4 to 1.8 shoots per subculture and total shoots produced per subculture after 12 weeks from 2.8 to 23.9. Rooting occurred readily on shoots isolated from E. purpurea cultures and was not promoted by addition of IBA to the rooting medium. Rooting was low and nil on shoots from cultures of E. angustifolia and E. pallida, respectively. Methods described in this study allow rapid multiplication of three Echinacea species and subsequent rooting of E. purpurea. Future improvements in root induction treatments will allow these methods to be used effectively for micropropagation and maintenance of disease-free germplasm of Echinacea species. Chemical names used: N-(pbenylmethyl)-1H-purine-6-amine (BA); 1H-indole-3-butyric acid (IBA).