Plant selection and virological tests: Before effecting the collection procedure, heathy and infected plants of E. purpurea grown in the open field at the Herb Garden of Casola Valsenio were selected and labelled by visual inspection of their aerial parts. The infection by CMV was associated with symptoms on both leaves and flowers. The most characteristic symptoms are yellow mosaic, ring and line-patterns on crinkled and deformed leaves that drop prematurely. The flowers, which may be smaller than normal, show color breaking with white or pale stripes on red petals. Shortening of the internodes is also very common, giving the plant a bushy appearance known as stunting. In Italian environmental conditions, these symptoms are best visible in the summer. On the other hand, plants appeared symptom-free were collected as healthy material. Plant collection: About 3-4 Kg fresh aerial part materials (70% stems, 10% leaves and 20% flowers) of healthy E. purpurea plants were collected in June 2000 at almost the end of flowering. An equivalent quantity of CMV-infected plants (evaluated by DAS-ELISA) was also collected; the percentage of leaves in the infected infected was about 6.0% as due to CMV presence that caused the premature leaf drop.

The oil from healthy material was rich in germacrene D (57.8%) and was more abundant. The infected materials afforded a lower oil content and significant quantitative variations in the oil composition. In particular, the observed percentage of germacrene D (52.6%) was reduced as were other sesquiterpene hydrocarbons. These variations, tested to be significant for all the compound-class fractions and individual major components, were ascribed to the cucumber mosaic cucumovirus (CMV) infection, the only fixed-effect variable that might affect the oil composition.