Grapevine rootstocks affect the biochemical and physiological responses of the scion evoked by water deficit condition

The selection of new grapevine rootstocks represents an important strategy for future agricultural managements for adaptation to climate changes. Recent studies highlighted the central role of the root system in modulating water stress (WS) responses. Not only roots control water uptake and transport towards leaves, but they also participate in stress perception and signalling to the shoot. In previous studies we reported the higher level of tolerance to WS of a new grapevine rootstock, named M4 [(V. vinifera × V. berlandieri) × V. berlandieri cv. Resseguier n. 1], as compared with the commercial rootstock 101.14. These studies employed the use of ungrafted plants. In the present study, we evaluated the performance of the two rootstocks in grafting combination with the cultivar Cabernet Sauvignon (Cab), by assessing the molecular, biochemical and physiological responses of the grafted plants to WS. The graft combination Cab/Cab was also included in the experimental design as control. WS was imposed by reducing water availability to 30% of the soil field capacity over a period of 10 days. Control plants were maintained at 80% of soil field capacity throughout the duration of the experiment. Our results show a greater WS tolerance in Cab/M4 respect to Cab/101.14 and Cab/Cab combinations, as demonstrated by the evaluation of biomass changes, CO2 assimilation (An), stomatal conductance (gs) and leaf water potential (leaf). Expression analyses of stress- and ABA-related genes as well as the determination of ABA levels in root and shoot organs highlighted differences among the graft combinations. Taken together, these results confirm (i) the central role of the root organ in regulating ABA-mediated stress responses and plant adaptation to WS and, (ii) the role of the M4 rootstock in enhancing the level of WS tolerance in the scion.