ABSTRACT
Plants have evolved an effective arsenal of defense mechanisms to cope with insect attacks. Some of these defenses are constitutive while others are induced after plant perception of stimuli associated with insect oviposition or herbivory. To date, a growing body of evidence has shown the possibility of enhancing the defense capabilities of plants by switching on relevant genes via the application of bioactive chemicals (so-called defense elicitors or inducers). Such manipulation of jasmonic acid (JA) and salicylic acid (SA) signalling can be a potential driver for innovation in crop protection against insect pests. However, most inducers promoting resistance to insect herbivores are still at the experimental level. Here, we investigated the effect of a plant defense activator, cis-jasmone (CJ), in a range of genotypes of Brassica napus, Brassica rapa and Brassica oleracea. Our results reveal that CJ treatment makes plants less attractive to aphid Myzus persicae but more attractive to parasitoid Diaeretiella rapae, in a wide range of brassica genotypes. It is likely that these effects are due to changes in volatile emission indicating the activation of defense and the presence of conspecific competitors to aphids but the presence of prey to parasitoids. These results build on earlier studies in Arabidopsis and show that tritrophic interactions are influenced by CJ in a wide range of brassica germplasm. The implication is that CJ is a promising treatment that could be used in Brassica crops as part of an integrated pest management system.
