A metabolomic approach to thrips resistance in tomato

Abstract

Western flower thrips is one of the most serious crop pests worldwide. Its control relies mainly on pesticides whose excessive use leads to resistance development and environmental contamination. As an alternative, in this thesis host-plant resistance in wild and domesticated tomatoes was studied using metabolomics. Different resistance mechanisms in which mechanical and chemical defenses work coordinately to fend thrips off were observed and contrasted. In all cases resistance was associated with the exudates of the glandular trichomes on the leaf surface. Different tomato species produce different exudates, mainly acylsugars, sesquiterpenes, methylketones and rutin. Surprisingly, the most effective and efficient defense mechanism was that observed among the domesticated tomatoes: polyphenol oxidase-catalyzed polymerization of rutin upon rupture of glandular trichomes literally welds thrips to the leaf surface. The genetics of chemically-based thrips resistance was also investigated using a chromosomal substitution set consisting of 76 introgression lines. Nine quantitative trait loci for thrips resistance and 268 for foliar metabolites were independently identified, but no chemical compounds in the lamella of tomato leaves could be identified as resistance factors against western flower thrips.