Somaclonal variation in solanaceous medicinal plants

A wide range of pharmaceutical secondary metabolites, derived from several higher plants, have been used to benefit mankind for many thousands of years. Many of these compounds have been known for years, and are still being used as the drugs of choice for specific therapy, e.g. Digitalis cardiac glycosides such as digoxin (Parr, 1989). Furthermore, new compounds are being isolated from the plant kingdom, and are actively screened. The chemical synthesis of most of the plant-derived compounds is possible; however, it is usually complicated, requires several steps in the biosynthetic pathway, and is thus uneconomical. Plant cell cultures offer an alternative approach to produce valuable plant compounds and they can also be used in plant breeding (Verpoorte et al., 1993). Plant tissue culture-derived variation among regenerated plants, or somaclonal variation, has been extensively studied, especially in crop plants such as sugarcane, tobacco, rice, maize and barley (Larkin and Scowcroft, 1981; Peschke and Phillips, 1992). However, surprisingly little information is available on the applications of somaclonal variation in medicinal plants and their cell cultures.