Direct and indirect plant defenses induced by (Z)-3-hexenol in tomato against whitefly attack

Plants have evolved induced defense mechanisms against insect herbivore attacks. The application of plant elicitors can enhance the biological control of crop pests by inducing plant defense responses, and (Z)-3-hexenol (z3HOL) is recognized as a herbivore-induced plant volatile that plays an important role in the chemical communication between plants and pests. We investigated whether z3HOL can activate the defense mechanism of tomato (Solanum lycopersicum) against the whitefly Bemisia tabaci, one of the major insect pests of cultivated tomato. Exposure to z3HOL vapors in the glass jars decreased weight gain and oviposition in B. tabaci and negatively influenced the feeding behavior of B. tabaci by shortening the total feeding period and phloem ingestion and increasing the frequency of stylet puncture. Furthermore, exposure to z3HOL induced jasmonic acid- and salicylic acid-mediated defense responses and enhanced B. tabaci-induced volatile emissions in tomato. The elevated release of tomato volatiles increased the attraction of the parasitoid Encarsia formosa and improved its parasitism on B. tabaci. Our results indicate that z3HOL can serve as an elicitor that triggers direct and indirect defense responses against B. tabaci by modulating signaling pathways in tomato. These findings will not only help us to gain a better understanding of how z3HOL influences the crop community, but also provide new insights into the potential application of z3HOL in integrated pest management systems.