Use of gas chromatograms of the essential leaf oils of the genus Eucalyptus for taxonomic purposes:: E. subser. Euglobulares (Blakely)

Leaves were harvested from 37 trees of Eucalyptus subser. Euglobulares Blakely, E. globulus Labill., E. bicostata Maiden, Blakely and Simmonds, E. maidenii F. Muell. and E. pseudoglobulus Naudin ex Maiden, selected from six sites around Australia: both native-growing and cultivated taxa were chosen. Volatile leaf oils were isolated by vacuum distillation and analysed by GC (one tree was previously analysed by GC-MS). The conditions of distillation and analysis were maintained throughout this study. Many of the taxa contained alpha-pinene (1.5-19.6%), limonene (1.0-5.1%), 1,8-cineole (39.3-71.7%), p-cymene (0.2-2.0%), pinocarvone (0.1-4.2%), beta-caryophyllene (0-5.5%), aromadendrene (0.9-20.3%), allo-aromadendrene (0.1-4.0%), alpha-terpineol (0.1-6.4%), globulol (0.1-5.5%), gamma-eudesmol (0-1.8%), alpha-eudesmol (0.1-5.6%) and beta-eudesmol (0.1-10.8%) as the main leaf oil components. The principal components analysis (PCA) and linear discriminant analysis (LDA) performed on the gas chromatograms of the 37 single trees studied revealed groupings of the taxa in approximate agreement with the results obtained from comparative morphological studies; LDA yielded four distinct groups, while PCA was not as discriminating. Nevertheless, in both cases the five pseudoglobulus trees formed distinct groups of their own. In addition, the loading factors of the PCA analysis indicated that the pseudoglobulus group was due to the presence in this taxon of large amounts of the three eudesmol oil components. Copyright (C) 2003 John Wiley Sons, Ltd.