High concentrations of sodium chloride (NaCl) in soil and water are increasingly common conditions in tomato (Solanum lycopersicum L.) production that impair the development and yield of this crop, generating the need for tolerant varieties. This research aimed to identify tomato lines tolerant to salinity during germination and early seedling development. A standard germination test was carried out in which 93 lines were evaluated under conditions of 0 and 80 mM NaCl for 12 days in a germination chamber with a temperature of 28 ± 1 °C and relative humidity of 80 ± 5%. At the seedling stage, 88 lines were evaluated under conditions of 0 and 150 mM NaCl in a floating raft system. During germination, saline conditions decreased germination percentage (37%), plumule (43%) and radicle (47%) length, dry matter (44%) and germination rate index (70%). At the seedling stage, NaCl decreased (p ≤ 0.05) plant height (44%) and leaf area (50%), without modifying root, aerial and total dry matter or root length. Twenty-eight tolerant lines were identified at germination and twenty-three at the seedling stage, seven of which were tolerant at both stages. This implies that salinity tolerance mechanisms differ in the developmental stages studied and makes it possible to combine these mechanisms to prolong tolerance during plant development.

Due to the widespread distribution of F. oxysporum, the search for mechanisms of tolerance to this disease in Solanum lycopersicum L. is an ongoing endeavor. This research aimed to identify F. oxysporum-tolerant genotypes at the germination and seedling stages in order to use them as sources of resistance. Ninety-six tomato lines were inoculated with the F. oxysporum strain with NCBI accession key PQ187438. The germination test was carried out in a germination chamber at a constant temperature of 28 ± 2 °C with 70 ± 5% relative humidity in darkness for the first 3 days and then 7 days with light. Clustering and discriminant analysis identified 14 genotypes with tolerance, showing great seed vigor and lower disease severity. Seedling evaluation was conducted in a floating raft system for 10 days after inoculation. Nine genotypes showed greater tolerance to the pathogen by developing a larger leaf area and accumulating more dry matter (p ≤ 0.05). No genotypes with tolerance were identified at both phenological stages (germination and seedling), indicating that tolerance mechanisms are independent at both phenological stages, so genotype selection should be carried out independently.