Salinity stress is a major abiotic factor limiting tomato (Solanum lycopersicum) production, particularly in arid and semi-arid regions. Utilizing genetic resources from wild tomato relatives, such as Solanum pennellii, through the exploitation of introgression lines (ILs) provides a promising strategy to enhance salt tolerance. This study evaluates the performance of nine tomato genotypes, including one commercial tomato hybrid (Formula F1) and eight ILs under three different soil salinity levels (1.88, 6.44, and 8.63 mS/cm), trying to identify salt-tolerant lines that maintain yield and fruit quality. Morphological characteristics, gas exchange parameters, yield traits, fruit quality characteristics, and antioxidant activity were assessed. High-performance liquid chromatography (HPLC) was employed to quantify the levels of carotenoids, namely lycopene and β-carotene, of fruits in selected genotypes. Additionally, total antioxidant capacity was measured in leaves, using DPPH, FRAP and FOLIN assays. The results indicate that out of all the evaluated characteristics, four plant-related traits, four fruit-related traits, one gas exchange parameter, and three productivity-related traits presented strong correlations to total yield (g/plant). These 12 traits could be considered as potential indexes for genotype salinity tolerance discrimination and could be utilized as an efficient marker tool for distinguishing tolerant genotypes to salinity stress, allowing breeders to reduce the time-consuming process of developing new salinity-tolerant varieties. Regarding genotypes’ ranking based on the relative performance of agronomic traits under a salinity regime of 8.63 mS/cm compared to a salinity regime of 1.88 mS/cm, IL6-6 exhibited significant tolerance to high-salinity conditions compared to the commercial hybrid and other ILs, like IL8-9. This tolerant IL maintained higher plant growth, yield, and fruit quality traits, including elevated levels in its fruits’ carotenoids and leaves’ antioxidant capacity, under severe salinity conditions, highlighting its potential for breeding programs targeting saline environments. ILs can help maintain productivity and fruit quality under salinity stress, making them a promising solution for sustainable tomato cultivation in salinity-affected regions. These findings, combined with previous results, suggest that tomato introgression lines offer a valuable genetic resource for developing tomato varieties suitable for harsh environments.
