cis-Jasmone induces tomato defense and affects oviposition preference of beet armyworm, Spodoptera exigua

The role of cis-jasmone (CJ) in priming plant defense against insect feeding is well documented in the literature. However, little is known about the role of CJ in mediating oviposition behavior of insects. Here we hypothesized that foliar application of CJ will prime induction of plant defense via enhanced emission of volatile organic compounds (VOCs), with negative consequences for insect oviposition. To test this hypothesis, headspace VOCs were collected and quantified from CJ-treated herbivore-damaged plants (CJD), untreated control herbivore-damaged plants (UD), CJ-treated healthy plants (CJ), and untreated control healthy plants (U). In addition CJD, UD, CJ, and U were presented to female Spodoptera exigua (a key pest of tomato) in oviposition dual choice tests. Finally, the transcript levels of key genes that encode VOC biosynthesis in the treatments were quantified. The results showed that most VOCs, including green leaf volatiles, monoterpenes, and sesquiterpene were emitted in significantly higher amounts in CJ-treated, herbivore-damaged plants compared with other treatments. Consequently, female S. exigua laid fewer eggs on CJ-treated, herbivore-damaged plants (29.95 %) compared to untreated herbivore-damaged plants (70.05 %). Moreover, the transcript levels of genes involved in VOCs biosynthesis were increased in CJ-treated plants infested with larvae than untreated control plants infested with larvae. These results indicate that exogenous application of CJ can prime tomato plant defense with potential ramifications for insects’ oviposition.