Metabolomics of Potato Genotypes with Contrasting Levels of Resistance to Late Blight

Potato (Solanum tuberosum L.) is the fourth most important food crop grown throughout the world. Late blight, caused by Phytophthora infestans is one of the most devastating diseases of potato. High cost fungicide application and race specificity are very challenging for breeders to develop resistant cultivars. The resistance in potato to late blight is either qualitative or quantitative in nature. Qualitative resistance is not durable but breeding for quantitative resistance is challenged by polygenic inheritence. Several quantitative trait loci (QTLs) have been identified but the mechanisms of resistance are largely unknown. The objective of this study was to identify resistance related metabolites, in a late blight resistant genotype, based on non-target metabolomics. A resistant (F06025) and a susceptible genotypes (Shepody) were inoculated, with pathogen or mock, and the metabolites were profiled using LC hybrid MS. The abundance of metabolites significantly higher in resistant than in susceptible were considered as resistance related metabolites. The  high fold change RR metabolites mainly belonged to three chemical groups: i) Phenylproponoids: 1-O-Feruloyl-beta-D-glucose, feruloyl agmatine, trans-beta-D-Glucosyl-2-hydroxycinnamate, 4-methoxy cinnamate, dihydroxyferuloyl-sinapoyl spermidine, tricoumaroyl spermidine; ii) Flavonoids: 7,4'-Dihydroxyflavone 7-rutinoside, kaempferol-3-rhamnoside-7-rhamnoside, isorhamnetin 3,4'-diglucoside, quercetin 3-(6'''-sinapylglucosyl)(1->2)-galactoside); iii) Fatty acid: 3-caproyl propionic acid. Most of the phenylpropanoids identified here are hydroxycinnamic acid amides, and these are known to be associated with cell wall appositions. These metabolites can be used as resistance biomarkers for screening cultivars against late blight following validation.