Effects of foliar applications of a proline-rich specific yeast derivative on physiological and productive performances of field-grown grapevines (Vitis vinifera L.)

The occurrence of heat waves in vineyards can damage the integrity of photosynthetic systems, impair yield and affect fruit quality. The frequency of these events is increasing due to global warming, and this is the subject of growing concern among the players in the wine sector. Canopy applications of specific yeast derivatives (SYD) are proposed to enhance plant physiology under abiotic stresses and preserve yield and fruit composition. This study aimed at assessing the effects of foliar application of a proline-rich SYD formulate, LalVigne ProHydro™ (LPH), on field-grown vines cv. Barbera. In a two-year experiment, vines subjected to multiple LPH foliar applications were compared to untreated vines (C). Gas exchange rates and vegetative and productive performances were monitored together with leaf proline, carotenoids and H2O2 concentrations. The data demonstrate that the formulate improved midday leaf water potential (+0.14 MPa), stomatal conductance (+0.15 mol m−2 s−1) and assimilation rates (+2.8 μmol m−2 s−1) under summer stress conditions. Interestingly, LPH leaves showed a dramatically higher concentration of proline (+600 %) and a significantly lower H2O2 content (-26 %) as compared to C leaves. The data suggest that this could be related to a priming effect of LPH application. Moreover, in SYD vines, cluster sunburn occurrence was reduced by 69 %, compared to C vines. At harvest, LPH improved vine yield (+1.27 kg), and LPH grapes had a significantly lower sugar concentration (-2.09 °Brix). The study demonstrates for the first time the potential benefits of proline-rich SYD application in vineyards subjected to multiple summer stress. Further studies should focus on the treatment effects on proline biosynthesis and gene expression.