Relative differences in salinity tolerance and genetic expression of salt‐tolerant and sensitive varieties of commercially important Solanaceae crops

Abstract Members of the Solanaceae family, such as tomatoes ( Solanum lycopersicum ), eggplants ( Solanum melongena L.), and peppers ( Capsicum chinense L.), are moderately sensitive to salinity, which could limit their production, especially under future water limitations and decreasing irrigation water quality. Heirloom cultivars provide valuable genetic resources for enhancing salinity resilience, yet their potential for intrinsic tolerance in Solanaceae crops remains unexplored. In this study, we built on earlier research by comparing relatively salt‐sensitive and salt‐tolerant cultivars of tomato, eggplant, and pepper under multiple salinity treatments using both chloride‐ and sulfate‐dominant irrigation waters. For each cultivar, we measured yield, biomass, ion concentrations, and gene expression profiles to gain insights into the mechanisms underlying salinity tolerance. The results indicate that these Solanaceae varieties may have higher salinity tolerance than reported in the literature (e.g., Food and Agriculture Organization Irrigation and Drainage Paper 61), with a notable increase in the yield reduction threshold for the sulfate treatments and potentially lower slope as assessed with the Maas–Hoffman model. Gene expression results revealed that salt‐tolerant cultivars in eggplant, tomato, and pepper (e.g., ‘Long Purple’, ‘Red Pear’, and ‘Ancho’) showed consistently more effective regulation of key Na + ‐ and Cl − ‐transport genes than their salt‐sensitive counterparts (e.g., ‘Black Beauty’, ‘Jaune Flamme’, and ‘Corbaci’). This included enhanced ion extrusion at the root surface, improved vacuolar sequestration of ions within cells, and tighter control over root‐to‐shoot ion movement. Together, these traits promoted tissue‐level tolerance by maintaining ionic homeostasis and preventing excessive ion accumulation. These results suggest that heirloom varieties are a potential genetic source for future plant breeding efforts to improve salinity tolerance in the “solanaceous” species studied.