Combined NMR and HPLC-HRMS metabolomics for discriminating the response of susceptible and resistant olive cultivars to Xylella fastidiosa infection

Bacterial infections caused by Xylella fastidiosa subsp. pauca ST53 (Xfp) in olives trigger the severe Olive Quick Decline Syndrome, one of the most severe threats to olive cultivation in the Mediterranean region. While the majority of the olive cultivars succumb to the infections by developing severe desiccation phenomena, only few exhibit resistance or tolerance responses. Current disease management strategies rely on vector control and the removal of infected sources, but these are only effective if these are timely implemented and on an area-wide base.¹ Therefore, the use of resistant or tolerant cultivars for the new plantations has been proposed as one of the most effective long-term mitigation strategies. Resistance refers to the ability of olive trees to limit the establishment and the rate of spread of the pathogen, whereas tolerance indicates the capacity to endure the damage caused by the pathogen without significant fitness loss.² Spectroscopy-based metabolomics has recently proven useful for investigating the biochemical changes associated with Xfp infection in olive trees.³⁻⁵ In this study, we applied a combined nuclear magnetic resonance (NMR) and high-performance liquid chromatography–high-resolution mass spectrometry (HPLC-HRMS) non-targeted metabolomics approach to investigate the metabolic alterations in xylem extracts from two olive cultivars, whose trees were grown under the same conditions, with contrasting phenotypes towards Xfp: FS17 (resistant/tolerant) and Arbequina (susceptible).⁶ The aim was to develop a robust metabolomics-based tool for effectively discriminating the metabolic response to infection and identifying potential biomarkers and metabolic pathways associated with resistance or tolerance mechanisms in olive trees