1H NMR Approach for Evaluating the Effects of a Natural Detergent on Olive Trees Infected by Xylella fastidiosa subsp. pauca

X. fastidiosa subsp. pauca (Xfp) is the etiological agent of “Olive Quick Decline Syndrome” (OQDS). Cellina di Nardò (Olea europaea L., Oleaceae), one of the major Salento cultivars, is highly susceptible to Xfp, usually showing acute symptoms after infection. NuovOlivo® a plant-derived formulation made with vegetal oils and water infusion from multi botanical species has been reported as effective against OQDS in plants affected by Xfp. A nontargeted 1H NMR (Nuclear Magnetic Resonance) fingerprinting approach, with unsupervised and supervised analysis, was applied to observe the possible changes in the metabolic profile in leaf samples of cultivars Cellina di Nardò naturally affected by Xfp treated with NuovOlivo® compared to untreated plants. The major differences were observed for the content of quinic acid, malate, mannitol, glucose, oleuropein, and aldehyde derivatives in treated compared to untreated samples. The resulting data indicated a seasondependent plant response to both disease and treatment. Moreover, the overall differences observed between the two investigated years, suggest a general decrease in the differences for the discriminating metabolites over time. The protocol NuovOlivo® was demonstrated to promote changes in the metabolic profile of olive leaves, suggesting a possible role of this treatment, integrated with good agricultural practices, against Xfp and OQDS.