Lychnophora pinaster Mart. (arnica; Asteraceae) is a native woody perennial species from Brazil endemic to the stony fields of the Brazilian Cerrado, a woodland savanna, where it grows as 0.4- to 2.4-m tall bushes. Flowering occurs from August to October and fruit dispersion in the months of December, January, and February. The flowers are lavender to crimson with a length of 8 to 10 mm (Semir, 1991). Its use as a topical application as a tincture of the aromatic leaves and flowers is considerable, owing to the antiinflammatory, anesthetic, and healing effects on bruises, sprains, and insect bites. Vegetative propagation of arnica using cuttings is somewhat troublesome because rooting is difficult. Furthermore, sexual reproduction is difficult as a result of the low viability of achenes (typically 2% to 5%). Both of these constraints encourage overharvesting of wild plants, leading to an extractive exploitation that exposes the species to the threat of extinction.
The interest in in vitro propagation of medicinal plants is clearly on the rise, because they represent the most important sources of medicines and other pharmaceutical products. Methods of in vitro propagation offer highly effective tools for germplasm conservation and mass multiplication of many plant species threatened with extinction (Murch et al., 2004; Pan et al., 2003).
Two strategies have been used for micropropagation of woody species: callus regeneration and bud multiplication. However, plant regeneration based on callus formation can have drawbacks in regard to the maintenance of desired genetic stability as a result of somaclonal variation (Jayasankar, 2000). In general, bud multiplication represents the most reliable method for vegetative propagation (Einset, 1991).
Bud multiplication has been successfully used for the medicinal species Pogostemon heyneanus (Hembrom et al., 2006), Lychnophora ericoides (Pereira et al., 2005), Decalepis hamiltonii (Giridhar et al., 2005), Clitoria ternatea (Rout, 2005), Rauvolfia tetraphylla (Faisal et al., 2005), Eclipta alba (Baskaran and Jayabalan, 2005), Rudgea viburnoides (Bonilla, 2002), Tournefortia paniculata (Bertolucci et al., 2000), and Echinodorus sp (Pereira et al., 2000).
Because micropropagation facilitates the establishment of a large number of plantlets in a relatively short period, and because there have been no studies on L. pinaster propagation, an attempt was made to develop protocols for micropropagation using nodal segments as well as plantlet development in different media for greenhouse acclimatization and field establishment.
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