Responses of the new grapevine rootstock M4 to drought : a biochemical and physiological characterization

In this study a new selected genotype, named M4, was compared with the commercial rootstock 101.14, analyzing the responses evoked by water stress (WS) in both the shoot and the root organs.The effects of progressive WS were studied in controlled environmental conditions on plants grown in pots.Sixty-six plants for each genotype were randomized to obtain two pools that were used as i) control, plants that were maintained at the 80% of the soil field capacity; ii) water stress, plants in which water supply was progressively reduced until the 30% of the field capacity. The effects of WS was studied for an experiment period of 10 days.Shoot growth, plant water status and leaf photosynthetic parameters were measured. Moreover, the levels of sugars, amino acids and total proteins as well as the contents of the more abundant ions were determined. M4 genotype resulted to have a greater capacity to tolerate WS, maintaining photosynthetic activity also under severe stress conditions. In this genotype, the root system appeared to play a central role to sustain biochemical and physiological responses evoked by WS, as suggested by the greater capacity to adequate inorganic and organic osmolytes in this organ. The experiments conducted in grafted plants, in which Cabernet was the used as scion, confirmed the good performances of M4.This study produced a first characterization of the new putative rootstock M4, in which the greater tolerance to WS, resulted strictly related to root integrity/functionality, so confirming that these aspects have to be considered in the further selection programs. Acknowledgments: Work was supported by SERRES-AGER project, grant n°2010-2105.