Herbivore‐induced volatiles of cabbage (<i>Brassica oleracea</i>) prime defence responses in neighbouring intact plants

<jats:title>Abstract</jats:title><jats:p>When attacked by herbivores, plants release herbivore‐induced plant volatiles (HIPV) that may function in direct defence by repelling herbivores or reducing their growth. Emission of HIPV may also contribute to indirect defence by attracting natural enemies of the herbivore. Here, cabbage (<jats:italic>Brassica oleracea</jats:italic> L.) plants (receiver plants) previously exposed to HIPV and subsequently induced through feeding by five <jats:italic>Pieris brassicae</jats:italic> L. caterpillars attracted more <jats:italic>Cotesia glomerata</jats:italic> L. parasitoids than control plants. HIPVs to which receiver plants had been exposed were emitted by <jats:italic>B. oleracea</jats:italic> infested with 50 <jats:italic>P. brassicae</jats:italic> caterpillars. Control plants had been exposed to volatiles from undamaged plants. In contrast, there were no differences in the attraction of wasps to receiver plants induced through feeding of one or ten larvae of <jats:italic>P. brassicae</jats:italic> compared to control plants. In addition, RT‐PCR demonstrated higher levels of <jats:italic>LIPOXYGENASE (BoLOX)</jats:italic> transcripts in HIPV‐exposed receiver plants. Exposure to HIPV from emitter plants significantly inhibited the growth rate of both <jats:italic>P. brassicae</jats:italic> and <jats:italic>Mamestra brassicae</jats:italic> caterpillars compared to growth rates of caterpillars feeding on control receiver plants. Our results demonstrate plant–plant signalling leading to priming of both indirect and direct defence in HIPV‐exposed <jats:italic>B. oleracea</jats:italic> plants.</jats:p>