Susceptible and resistant olive cultivars show differential physiological response to Xylella fastidiosa infections

Abstract

Olive quick decline syndrome (OQDS) is a severe disease, first described in Italy in late 2013, caused by strains ofXylella fastidiosasubsp.pauca (Xfp)in susceptible olive cultivars. Conversely, resistant olive cultivars do not develop OQDS but present scattered branch dieback, which generally does not evolve to severe canopy decline. In the present study, we assessed the physiological responses ofXfp-infected olive trees of susceptible and resistant cultivars. Periodic measurements of stomatal conductance (gs) and stem water potential (Ψstem) were performed using a set of healthy andXfp-infected plants of the susceptible “Cellina di Nardò” and resistant “Leccino” and “FS17” cultivars. Strong differences in Δgsand ΔΨstem amongXfp-infected trees of these cultivars were found, with higher values in Cellina di Nardò than in Leccino and FS17, while no differences were found among healthy plants of the different cultivars. Both resistant olive cultivars showed lower water stress uponXfpinfections, compared to the susceptible one, suggesting that measurements of gsand Ψstem may represent discriminating parameters to be exploited in screening programs of olive genotypes for resistance toX. fastidiosa.