How rootstocks influence salt tolerance in grapevine? The roles of conferred vigor and ionic exclusion

The aim of this work was to evaluate whether selected grapevine rootstocks can confer greater salt tolerance than own-rooted Vitis vinifera L. A trial was carried out with potted own-rooted 'Malbec' vines and also grafted onto three rootstocks (101-14 Mgt, 1103P and Cereza). Aditionally, the vines were irrigated with a solution containing 0, 50 and 100 mM NaCl. Vegetative growth was the most sensitive variable to salinity and was affected even at 50 mM. Above 0.1% dw Na⁺ and 0.6% dw Cl^-, the leaf area was negatively correlated with Na⁺ and Cl^- in leaf blades. Membrane integrity and chlorophyll content in leaves were affected only at 100 mM. At 50 mM, 1103P showed a decrease in leaf area but this parameter was not further affected at 100 mM. Own-rooted and 1103P vines showed fewer visual symptoms of toxicity and maintained higher leaf area (+450% higher relative to 101-14 Mgt) and higher membrane integrity (+81% higher relative to Cereza) at high salinity. Own-rooted and 1103P vines grown in 0 mM NaCl also showed higher leaf area and biomass production (i.e., vigor), suggesting that salt tolerance is linked to innate vigor. Regardless of the NaCl content, 101-14Mgt showed higher Na⁺ concentration in leaf blades than own-rooted and 1103P vines (+266%). At 50 mM, Cereza concentrated more Cl^- than the others (+114%). At 100 mM, Cereza and 101-14 Mgt concentrated more Cl^- than both 1103P and own-rooted vines (+133%). The 1103P limited the entry of Na⁺ and Cl^- to the vines more than the others (-58 and -62% respectively), suggesting a higher exclusion capacity. The results suggest that the use of own-rooted 'Malbec' remains as a viable alternative under high soil salinity conditions. The use of the 1103P rootstock also appears as an alternative due to its excluding behavior.