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 ante nnae of the tobacco budworm moth Heliothis virescens were screened for sens itivity to naturally occurring plant-produced volatiles by the use of gas c hromatography linked to electrophysiology. Volatiles of host as well as non -host: plants collected by headspace techniques were used for stimulating t he neurones, sequentially via two columns, one polar and one nonpolar insta lled in parallel in the gas chromatograph. Three types of neurones presente d in this paper responded to one, two or three compounds for which the rete ntion times were determined ill 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 a nd homo-farnesene for neurone type 3. Re-testing authentic materials verifi ed the identifications for the type I neurones. The results demonstrate a h igh specificity for the three types of neurones by strong responses to one or two structurally similar compounds out of hundreds present in a large va riety of plants. The study exemplifies plant odour detection by narrowly tu ned receptor neurones in a polyphagous moth species.