Structural Barriers Against Xylella: Cell Wall Strategies in Olive Resistance

Xylella fastidiosa (Xf) is a xylem-limited bacterial pathogen and the causal agent of Olive Quick Decline Syndrome (OQDS), a devastating disease severely affecting olive groves, particularly in the Mediterranean region. Although some cultivars exhibit resistance to Xf, the underlying molecular and structural mechanisms remain poorly understood. Recent studies have shown that phenolic extracts from olive mill waste exhibit antimicrobial activity against Xf and stimulate innate immunity in plants (Greco et al., 2024). Additionally, increasing evidence suggests a crucial role of the plant cell wall (CW) both as a physical barrier and as an active component of plant immunity. In this study, we investigated CW structural traits in resistant (FS17) and susceptible (Arbequina) olive cultivars in response to Xf infection. Our findings indicate resistance involves active reinforcement of specific CW components. Overall, our results underscore the role of cultivar-specific CW dynamics in determining resistance outcomes and offer insights for breeding programs aimed at improving tolerance to Xf.