Selective receptor neurone responses to E-beta-ocimene, beta-myrcene, E,E-alpha-farnesene and homo-farnesene in the moth Heliothis virescens, identified by gas chromatography linked to electrophysiology.

An important question in olfaction is for which odorants receptor neurones have evolved. In the present study, olfactory receptor neurones on the antennae of the tobacco budworm moth Heliothis virescens were screened for sensitivity to naturally occurring plant-produced volatiles by the use of gas chromatography linked to electrophysiology. Volatiles of host as well as non-host plants collected by headspace techniques were used for stimulating the neurones, sequentially via two columns, one polar and one nonpolar installed in parallel in the gas chromatograph. Three types of neurones presented in this paper responded to one, two or three compounds for which the retention times were determined in both column types. The chemical structures of the active components were determined on the basis of mass spectrometry linked to gas chromatography, indicating E-beta-ocimene and beta-myrcene as stimulants for neurone type 1, E,E-alpha-farnesene for neurone type 2 and homo-farnesene for neurone type 3. Re-testing authentic materials verified the identifications for the type 1 neurones. The results demonstrate a high specificity for the three types of neurones by strong responses to one or two structurally similar compounds out of hundreds present in a large variety of plants. The study exemplifies plant odour detection by narrowly tuned receptor neurones in a polyphagous moth species.