Physiological and Biochemical Responses of Grafted Tomato Plants to Salinity Stress: Evidence from the Syrian Coast

The research was carried out in Tartus (Syria), in a plastic greenhouse during the season 2024-2025. Two tomato hybrids "Levovil and Shannon" were grafted onto two tomato "Spirit and Maxifort" rootstocks. Four levels of salinity (0, 50, 100 and 150 mM NaCl) were applied on the hybrids and grafted plants. Salinty stress induced physiological and biochemical changes in plant. At salinity level of 150 mM, the absolute value of the osmotic pressure increased to -1.18 and -1.12 Mpa, in Levovil and Shannon hybrids, as compared to -0.80 and - 0.74 Mpa in the controls, respectively. While 150 mM salinity level led to an increase of the contents of dry matter, proline, sugars and chlorine, it caused a decrease of K: Na ratio in the two hybrids (1.99 and 1.8) as compared to the controls (5.29 and 4.68, respectively). The salinity stress at 150 mM, reduced the yield of the two hybrids (26.26 and 25.28 kg/m2) as compared to the controls (33.90 and 33.11 kg/m2, respectively). The tomato scions "Levovil and Shannon hybrids" grafted onto the "Spirit and Maxifort" rootstocks enhanced the osmotic adjustment phenomenon, especially when the two hybrids were grafted onto Spirit. While tomato grafting had a significant effect on the accumulation of some osmotic compounds such as proline and sugars, in addition to increasing K: Na ratio, it reduced the absolute value of the osmotic pressure of the plant and its sodium content. Therefore, the yield increased in grafted tomato plants compared with non-grafted plants under saline conditions. The results of PCA analysis showed that the first two principal components (PC1 and PC2) explained 89.08% of the total variation, wherease all the studied parameters were well represented. The dendrogram was obtained based on the same variables as PCA, and it led to classify "Spirit" rootstock as tolerant to salt stress, "Maxifort" rootstock as half tolerant, and the non-grafted hybrids "Levovil and Shannon" as sensitive to salt stress.