Rootstock varietal ability in accumulation of chloride ions underpins improved physiology and metabolism of grapevine exposed to salinity

Soil salinity limits plant growth, affects crop production and nutrition, and endangers food security globally. The use of salt-tolerant rootstocks has proven to be an efficient strategy to alleviate the adverse effects of salinity in different crop species including Vitis vinferae. The long-term response to salinity of three grapevine rootstock varieties, Paulsen 1103 (P1103), Richter 110 (R110), and Sélection Oppenheim 4 (SO4), was tested in pots with drip irrigation at different NaCl concentrations (0, 10 mM, and 30 mM) for 82 days. During the experiment, plant morphology, physiology, and central metabolism were monitored. The results revealed that shoot growth, including stem diameter and fresh and dry weight of stems and leaves, was significantly restricted by salinity in P1103 and SO4, less in R110. Roots were more sensitive than shoots to salinity, showing significant reductions in biomass already at 10 mM NaCl. The high salinity level markedly reduced most of the photosynthetic traits measured in P1103 and R110. In contrast, SO4 was exceptionally stable from a physiological standpoint, while having the lowest chloride contents in its leaves compared to the other two varieties when exposed to salinity. Elemental analysis and GC-MS based metabolite profiling of the leaves exposed to a salt stress revealed a shift in carbon (C) and nitrogen (N) metabolism, reflected by a decreased C: N ratio and by a lower content of organic acids (e.g. succinate, malate, and citrate) likely supporting the measured accumulation of amino acids (e.g. GABA, glutamate, and proline) in P1103 and R110. In addition, correlation-based network analysis (CNA) of the metabolic data revealed increased coordination of metabolic processes under salinity than under control conditions. CNA also showed higher alteration in the metabolic network in P1103 and R110 than in SO4. Taken together, the results reveal that SO4 showed milder alteration in its photosynthetic and metabolic response to saline conditions, in association with lower Cl⁻accumulation in its leaves.