Open access publications in the SLU publication database

Abstract

It is well known that volatile cues from damaged plants may induce resistance in
neighboring plants. Much less is known about the effects of volatile interaction between
undamaged plants. In this study, barley plants, Hordeum vulgare cv. Kara, were exposed
to volatiles from undamaged plants of barley cv. Alva or thistle Cirsium vulgare, and
to the volatile phytochemicals, methyl salicylate or methyl jasmonate. Exposures were
made either during natural daylight or darkness. Acceptance of exposed plants by the
aphid Rhopalosiphum padi was assessed, as well as the expression of putative marker
genes for the different treatments. Aphid acceptance of plants exposed to either barley or
C. vulgare was significantly reduced, and an effect of the volatiles from undamaged
plants was confirmed by the induction of pathogenesis‑related protein, PR1a in exposed
plants. However the effect on aphid acceptance was seen only when plants were exposed
during darkness, whereas PR1a was induced only after treatment during daylight. Aphid
acceptance of plants exposed to either methyl salicylate or methyl jasmonate was significantly
reduced, but only when plants were exposed to the chemicals during daylight.
AOS2 (allene oxide synthase) was induced by methyl jasmonate and BCI‑4 (barley
chemical inducible gene‑4) by methyl salicylate in both daylight and darkness. It is
concluded that (a) the effects on aphids of exposing barley to volatile phytochemicals was
influenced by