Metabolomic characterization of xylem sap of different olive cultivars growing in Spain

Abstract

With the goal of understanding the nutritional requirements of xylem-limited microbiome, the chemical composition of xylem sap extracted from two Olea europaea var. europaea cultivars (Picual and Arbequina) was evaluated. Selected plants were established on their own feet or grafted onto rootstocks of Olea europaea var. sylvestris. Xylem sap of olives branches was collected using a external 45-cm external Scholander Super Chamber. Metabolome analysis was performed by proton nuclear magnetic resonance (NMR) spectroscopy-based study and the ionome analysis was performed by inductively coupled plasma with optical emission spectroscopy (ICP-OES). In total 26 metabolites were identified by NMR spectroscopy, including amino acids (alanine, arginine, aspartate, glutamate, glutamine, isoleucine, leucine, methionine, proline, threonine, tyrosine, and valine), sugars (glucose, fructose, mannitol, myo-inositol, and sucrose), organic acids (formic, fumaric and succinic acid), alcohols (ethanol and methanol), and other molecules. On the other hand ICP-OES allowed the quantification of 14 elements and five inorganic anions. Xylem sap analysis will lead to a better understanding of the biology and complex nutritional requirements of olive xylem-inhabiting microorganisms, including Xylella fastidiosa, and to help designing artificial growing media to improve culturing of the olive microbiome.