Characterizing the volatilome and transcriptome of resistant and susceptible tomato cultivars in response to two-spotted spider mite infestation reveals the constitutive and inducible patterns of monoterpenoids

Two-spotted spider mites (TSSM; Tetranychus urticae) ) is a ubiquitous polyphagous arthropod herbivore and a major pest in greenhouses, fields, and orchard crops worldwide. In response to TSSM attack, tomato plants (Solanum lycopersicum), produce a blend of volatile molecules, such as terpenoids. Some of these volatiles have insecticidal activity and some are known to attract natural enemies of the herbivores. The main goal of our research is to characterize volatiles composition and emission of tomato plants in response to TSSM infestation and to identify volatile molecules involved in tolerance mechanism to TSSM. To address this, we analyzed transcriptomic and metabolite responses of two cherry tomato cultivars, which showed different mite resistant phenotype. The findings reveal that the resistant cultivar possessed more monoterpenes in different development stages. Few of the monoterpenes such as alpha-Terpinene, beta-Phellandrene and Limonene were significantly more abundant in the resistant cultivar. We investigated the gene expression of Terpenes Synthases between the two cultivars and found remarkable differences in the expression of TPS7 and TPS20, enzymes that catalyze the formation of monoterpenes, mostly beta-Myrcene, Limonene and beta-Phellandrene. This study highlights the function of terpenoids on plant resistanceto spider mite and might provide some important guidelines for developing new improved tomato cultivars.