Metabolomics of Thrips Resistance in Pepper (Capsicum spp.) Reveals Monomer and Dimer Acyclic Diterpene Glycosides as Potential Chemical Defenses

The development of pesticide resistance in insects and recent bans on pesticides call for the identification of natural sources ofresistance in crops. Here, we used natural variation in pepper (Capsicum spp.) resistance combined with an untargeted metabolomicsapproach to detect secondary metabolites related to thrips (Frankliniella occidentalis) resistance. Using leaf disc choiceassays, we tested 11 Capsicum accessions of C. annuum and C. chinense in both vegetative and flowering stages for thripsresistance. Metabolites in the leaves of these 11 accessions were analyzed using LC-MS based untargeted metabolomics. Thechoice assays showed significant differences among the accessions in thrips feeding damage. The level of resistance depended onplant developmental stage. Metabolomics analyses showed differences in metabolomes among the Capsicum species and plantdevelopmental stages. Moreover, metabolomic profiles of resistant and susceptible accessions differed. Monomer and dimeracyclic diterpene glycosides (capsianosides) were pinpointed as metabolites that were related to thrips resistance. Sucrose andmalonylated flavone glycosides were related to susceptibility. To our knowledge, this is the first time that dimer capsianosides ofpepper have been linked to insect resistance. Our results show the potential of untargeted metabolomics as a tool for discoveringmetabolites that are important in plant – insect interactions.Keywords Capsianosides . Frankliniella occidentalis . Liquid chromatography-mass spectrometry . Insects . Solanaceae . Thrip