Effect of Different Rootstocks on the Salt Stress Tolerance and Fruit Quality of Grafted Eggplants (Solanum melongena L.)

Vegetable grafting is considered a rapid, non-chemical alternative method to relatively slow and expensive breeding to overcome the adverse effect of salinity. Therefore, a soilless experiment was performed to determine the salinity tolerance of eggplant (Solanum melongena) cv. Madonna grafted onto two different rootstocks, Solanum grandifolium × Solanum melongena (SH) and Solanum torvum (ST), as well as self-grafted (SG) and self-rooted (SR) as controls. All groups of plants were treated with 0 mM NaCl or 80 mM NaCl. A significant decrease in the relative leaf chlorophyll content (SPAD value) and chlorophyll concentrations were found in response to NaCl. However, the grafted plants had a higher photosynthetic pigment level than the non-grafted plants grown under saline conditions. Grafting eggplants onto SH significantly enhanced the total fruit yield as compared to the self-rooted plants exposed to salinity by increasing the average fruit weight. Moreover, salt stress significantly increased the whitening index and oxidation potential of fruits. The plants grafted onto SH or ST accumulated more Na⁺ in their roots than in their fruit or leaves, thus the Na⁺ partitioning between the above-ground and root parts most probably determines the increased salinity tolerance of the grafted ST and SH plants. To conclude, both the SH and ST rootstocks protected the scions against salinity; the scion showed both increased photosynthetic pigment concentration and chlorophyll fluorescence parameters as well as a lower Na⁺ concentration under stress that resulted in a higher fruit yield and quality.