We evaluated the salt tolerance of eggplant cv Angela, under both non-grafted conditions and when grafted on tomato cv Maxifort rootstock, at 5 salinity levels and two water composition types (up to 0.6 MPa osmotic potential). We salinized the irrigation water with either a Na⁺-Ca²⁺- Cl^- composition typical of coastal Mediterranean ground waters as well as a mixed Na⁺-Ca²⁺-SO₄^2- Cl^- type water a composition more typical of interior continental basin ground waters such as those of the Central Valley California, U.S.A.

There were statistically significant differences in the fruit yield relative to the water type, with Cl^- type waters having less yield, indicating that Cl^- concentration is a factor in eggplant yield associated with salinity. Grafted eggplant exhibited large increased yield both under control and elevated salinity levels relative to non-grafted plants. In addition to absolute yield relationships, the expression of salt tolerance in terms of relative yield provides the conclusion that grafted plants are more salt tolerant than non-grafted plants. For example at osmotic potential of -0.30 MPa, (EC=8.26 dS/m) the grafted plants had a relative yield of 47% (5.21 kg/plant fresh weight ) while the non-grafted plants had a relative yield of 19% (1.66 kg/plant). Leaf and fruit Na concentration increased with increased salinity as expected. Eggplant grafted on Big Dena tomato rootstock had significantly lower leaf and fruit Na concentrations as compared to non-grafted eggplant under saline treatments. Leaf Na for the grafted plants ranged from 52 mmol/kg dry weight at OP=-0.15 MPa to 144 mmol/kg at OP=-0.60MPa (EC=15.8 dS/m) while the corresponding range for non-grafted plants was 76 and 365 mmol/kg, respectively. These data suggest that the explanation for the increased salt tolerance of the grafted plants is related to restriction of leaf Na concentration. Elevated leaf Na is known to reduce photosynthetic activity.   

Keywords: Chloride salinity, Grafting, Irrigation, Salt tolerance, Sulfate salinity, Eggplant