Characterization and Potential Role of Fatty Acid-Solamine Conjugates in Plant Defense against Herbivores and Pathogens in Wild Potato Species

The fatty acid-solamine conjugate C16:3(7Z,10Z,13Z)-solamine was isolated from leaves of the wild potato species Solanum bulbocastanum and structurally characterized using spectroscopic methods. The exogenous application of C16:3(7Z,10Z,13Z)-solamine reduced the feeding of Colorado potato beetles (Leptinotarsa decemlineata) and potato flea beetles (Epitrix papa) on Solanum tuberosum leaf disks and inhibited the germination of sporangia produced by the oomycete pathogen Phytophthora infestans and subsequent plant infection. The use of liquid chromatography-coupled tandem mass spectrometry enabled the detection and characterization of numerous acyl solamines in S. bulbocastanum leaves and in the belowground organs of numerous accessions of eight wild potato species and of cultivars of S. tuberosum. The annotated acyl solamines comprise medium- and long-chain fatty acyl solamines, whose acyl groups differ in chain length, the number of double bond equivalents, and the number of oxygenations, as well as hydroxycinnamoyl solamines. The profiles of the detected acyl solamines exhibited notable variation between different Solanum species, as well as between different tissues within a species. The potential role of acyl solamines in plant defense and their potential utility in plant protection and resistance breeding are discussed.