Broad spectrum insect resistance and metabolites in close relatives of the cultivated tomato

Abstract

Wild relatives of tomato possess effective means to deal with several pests, among which are a variety of insects. Here we studied the presence of resistance components against Trialeurodes vaporariorum, Myzus persicae, Frankliniella occidentalis, and Spodoptera exigua in the Lycopersicon group of Solanum section Lycopersicon by means of bioassays and comprehensive metabolite profiling. Broad spectrum resistance was found in Solanum galapagense and a few accessions of S. pimpinellifolium. Resistance to the sap sucking insects may be based on the same mechanism, but different from the caterpillar resistance. Large and highly significant differences in the leaf metabolomes were found between S. galapagense, containing type IV trichomes, and its closest relative S. cheesmaniae, which lacks type IV trichomes. The most evident differences were the relatively high levels of different methylated forms of the flavonoid myricetin and many acyl sucrose structures in S. galapagense. Possible candidate genes regulating the production of these compounds were identified in the Wf-1 QTL region of S. galapagense, which was previously shown to confer resistance to the whitefly B. tabaci. The broad spectrum insect resistance identified in S. galapagense will be very useful to increase resistance in cultivated tomato.

QTL mapping of insect resistance components of Solanum galapagense

“…Leaves were flash-frozen in liquid nitrogen and stored at − 80 °C until use. Samples were processed for liquid chromatography–mass spectrometry (LC–MS) in acidified aqueous methanol as described previously (Vosman et al 2018). A Waters Acquity HPLC coupled to a Thermo Ion Trap-Orbitrap FTMS hybrid MS system operating in negative electrospray ionization mode, a Phenomenex Luna C18 (2) column and a gradient of water and acetonitrile, both acidified with 0.1% FA, were used as described by Firdaus et al (2013).…”

“…A Waters Acquity HPLC coupled to a Thermo Ion Trap-Orbitrap FTMS hybrid MS system operating in negative electrospray ionization mode, a Phenomenex Luna C18 (2) column and a gradient of water and acetonitrile, both acidified with 0.1% FA, were used as described by Firdaus et al (2013). Data processing and analysis was carried out in an essentially untargeted manner using the Metalign-MSClust workflow as described by Vosman et al (2018), resulting in a large spreadsheet with the relative intensity of each compound detected, either known or yet unknown, in each sample. Both sucrose- and glucose-based acyl sugars with 2, 3 or 4 acyl chains were annotated based on their specific accurate masses and retention times (Vosman et al 2018), using the mass of the formic acid adduct generated in the mass spectrometer as this [M + CH 2 O 2 –H] − adduct signal was considerably higher than its original [M–H] − molecular ion.…”

“…Data processing and analysis was carried out in an essentially untargeted manner using the Metalign-MSClust workflow as described by Vosman et al (2018), resulting in a large spreadsheet with the relative intensity of each compound detected, either known or yet unknown, in each sample. Both sucrose- and glucose-based acyl sugars with 2, 3 or 4 acyl chains were annotated based on their specific accurate masses and retention times (Vosman et al 2018), using the mass of the formic acid adduct generated in the mass spectrometer as this [M + CH 2 O 2 –H] − adduct signal was considerably higher than its original [M–H] − molecular ion. Only metabolites that were detected in at least 20% of the population were considered in the QTL analysis described below.…”

“…Data analysis was carried out according to Vosman et al (2018). Survival was expressed as (living whiteflies)/(living + dead whiteflies).…”

“…Metabolite data: Data analysis was carried out essentially as described by Vosman et al (2018). In case a metabolite was not detected in a sample, a random value between 400 and 500 (45–55% of the detection threshold value) was assigned in the data matrix.…”