Previous studies have demonstrated that the widely distributed desert plant Eremophila longifolia has at least six geographically defined
essential oil chemotypes. The focus of the present study is to extend and enhance information concerning known chemotypes and to investigate the involvement of cell nuclei ploidy in this variation. Forty field collected specimens of E. longifolia were taken from most of the mainland states of Australia then subjected to hydrodistillation to produce
essential oils, which were then chemically characterised. Ploidy was determined using relative fluorescence of cell nuclei stained with
propidium iodide, measured in a flow cytometer. Using principal component analysis (PCA), at least three
essential oil chemotypes, in addition to the six already described, were identified in the present study. Previously described high yielding
essential oil chemotypes were also characterised in terms of diploidy. For the first time diploid populations were identified in New South Wales, correlating with high yielding
isomenthone/
menthone and karahanaenone chemotypes. Furthermore, the separate diploid population previously described from Western Australia was demonstrated to be the
safrole/
methyl eugenol type, which is restricted to a small geographic range in far north-west Western Australia (Murchison District). All other chemotypes were shown to be
tetraploid, including apparently randomly emerging individuals, representative of chemotypes producing low yields of
isomenthone/
menthone and karahanaenone similar in composition to the high yielding diploid types.