The identification of acylsugars as a resistance factor for thrips in tomato proves that NMR-based metabolomics an important tool to study plant defences, providing fundamental information for the development and realisation of herbivore resistance breeding programmes in agricultural crops.

IntroductionTo date, most studies of natural variation and metabolite quantitative trait loci (mQTL) in tomato have focused on fruit metabolism, leaving aside the identification of genomic regions involved in the regulation of leaf metabolism.ObjectiveThis study was conducted to identify leaf mQTL in tomato and to assess the association of leaf metabolites and physiological traits with the metabolite levels from other tissues.MethodsThe analysis of components of leaf metabolism was performed by phenotypying 76 tomato ILs with chromosome segments of the wild species Solanum pennellii in the genetic background of a cultivated tomato (S. lycopersicum) variety M82. The plants were cultivated in two different environments in independent years and samples were harvested from mature leaves of non-flowering plants at the middle of the light period. The non-targeted metabolite profiling was obtained by gas chromatography time-of-flight mass spectrometry (GC-TOF-MS). With the data set obtained in this study and already published metabolomics data from seed and fruit, we performed QTL mapping, heritability and correlation analyses.ResultsChanges in metabolite contents were evident in the ILs that are potentially important with respect to stress responses and plant physiology. By analyzing the obtained data, we identified 42 positive and 76 negative mQTL involved in carbon and nitrogen metabolism.ConclusionsOverall, these findings allowed the identification of S. lycopersicum genome regions involved in the regulation of leaf primary carbon and nitrogen metabolism, as well as the association of leaf metabolites with metabolites from seeds and fruits.Electronic supplementary materialThe online version of this article (10.1007/s11306-019-1503-8) contains supplementary material, which is available to authorized users.

Invasion of pests may result in local adaptation and the development of biotypes specialized in different hosts. In this study, we investigated western flower thrips, Frankliniella occidentalis (Pergande), an invasive pest in Europe. Thrips from different commercial glasshouse crops within the Dutch Westland and a lab culture kept on chrysanthemum were compared. Genetic barcoding was applied for the identification of potential western flower thrips cryptic species in the Netherlands revealing that all western flower thrips populations studied belonged to the "glasshouse" strain reported in California as the only existing species in the Netherlands. Feeding and reproduction parameters in leaf disc and whole plant bioassays were scored. We detected significant differences in thrips feeding among host plants and thrips origin. Host plants differed in average thrips damage while thrips from different origins caused similar amounts of damage across host plants. In contrast, reproductive success of thrips on all plant species depended strongly on thrips origin. The thrips lab culture maintained on chrysanthemum obtained the highest levels of reproduction on chrysanthemum. Differences among the other thrips populations were relatively small. Amplified fragment length polymorphisms analyses were used to study genetic differences between western flower thrips populations and confirmed that the lab culture population was also genetically the most different of all studied populations. The results of the amplified fragment length polymorphisms analyses together with the better reproductive performance of thrips on the host plant on which they were maintained demonstrate the evolution of a lab biotype specialized in a particular host. This finding has potential relevance for future crop control and breeding programs.

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