Differential gene expression in two grapevine cultivars recovered from "flavescence dorée"

The biological bases of recovery of two grapevine cultivars, Nebbiolo and Barbera, showing different susceptibilityand recovery ability to "flavescence dorée" (FD) phytoplasma infection were investigated. The expressionover one vegetative season, in FD-recovered and healthy grapevines, of 18 genes involved in defence, hydrogenperoxide and hormone production was verified at two time points. Difference (?) between the relative expressionsof August and July were calculated for each target gene of both cultivars. The significance of differencesamong groups assessed by univariate and multivariate statistical methods, and sPLS-DA analyses of the ?gene expression values, showed that control and recovered grapevines of both cultivars were clearly separated.The Barbera-specific deregulation of defence genes supports a stronger response of this variety, within a generalframe of interactions among H2O, jasmonate and ethylene metabolisms, common to both varieties. This maystrengthen the hypothesis that FD-recovered Barbera grapevines modulate transcription of their genes to copewith potential damages associated to the alteration of their oxidative status. Nebbiolo variety would fit into thispicture, although with a less intense response, in line with its lower degree of susceptibility and recovery incidenceto FD, compared to Barbera. The results evidenced a scenario where plant response to phytoplasmainfection is highly affected by climatic and edaphic conditions. Nevertheless, even after several years from theoriginal FD infection, it was still possible to distinguish, at molecular level, control and recovered grapevines ofboth cultivars by analyzing their overall-season response, rather than that of a single time point.2