Exploring different phenotypic and molecular approaches to unravel early events in olive-Xylella interactions

Xylella fastidiosa is a xylem-limited plant-pathogenic bacterium causing severe diseases in several crops. Infections in olives cause the olive quick decline syndrome, a disease that compromises the survival of susceptible trees. This represents one of the most challenging pathosystems to study, because infections have a long incubation period (i.e. > 1 year before any visual alteration induced by the bacterium can be detected) and bacterial virulence factors/host response mechanisms are largely unknown. Even so, it is extensively documented that the formation of cell aggregates in the vessels and the degradation of the cell wall cause the hydraulic collapse of the xylem network. Such phenomena are more prominent in the susceptible hosts, while resistant/tolerant genotypes may remain symptomless or show mild symptoms. We aimed to explore the use of different physiological traits, that combined with molecular markers, may identify biomarkers suitable for the early prediction of the host response. Phenotypic measurements likewise stomatal conductance, stem water potential, leaf and canopy temperature, electrical signal changes in the sap flux monitored by electrical impedance spectroscopy and massive transcriptomic data have been generated from plants under different infection conditions. Efforts are directed to integrate transcriptomic and physiological data, in a multiomic approach, for rapid and accurate predictions of resistant vs susceptible phenotype.