Cardenolide variation within and among natural populations of Digitalis obscura

Cardenolide content in 43 wild-growing Digitalis obscura plants from six natural populations on the Iberian Peninsula was determined by HPLC. Series A and B glycosides were the predominant cardenolides in all samples, but absolute values varied among and within populations. Hierarchic analysis of variance showed that the proportion of variation attributable to individuals was significantly higher than that attributable to population differences. Furthermore, analyses from greenhouse-grown plants, generated from seeds collected from selected parental genotypes, attributed nearly all the variability in cardenolide content to single plants. Some individual planes showed a leaf content above 3500 mu g/g dry wt of series A and B cardenolides and will be selected for genetic improvement of Digitalis obscura.