Physiological and metabolic profiling reveals distinct early salt resilience strategies among pre-commercial broccoli cultivars

• Coordinated physiological and metabolic responses drive broccoli salt resilience. • A conservative water-use strategy prevents salinity-induced dehydration in BQ1. • Leaf retention of phosphorous and boron supports cellular integrity under ionic stress. • Sucrose and maltose accumulation fuels energy metabolism for salt adaptation. • Early antioxidant induction mitigates oxidative damage during initial stress. Soil salinization represents a primary abiotic constraint to global agricultural productivity, necessitating the development of resilient cultivars. This study assesses the physiological and metabolic responses associated with salinity tolerance in four pre-commercial broccoli ( Brassica oleracea var. italica ) cultivars (BG1, BH1, BX1, and BQ1) during the vegetative stage under salt stress conditions. Among the genotypes, BQ1 demonstrated superior performance at the lowest salinity level assayed (80 mM NaCl), maintaining biomass accumulation and the highest Salt Tolerance Index (STI). This resilience is attributed to a constitutive physiological adaptation characterized by a low stable relative water content (RWC) and water potential, which prevents further salinity-induced dehydration. Furthermore, BQ1 exhibited effective ionic homeostasis by retaining phosphorus (P) and boron (B) in root tissues, alongside an early induction of ascorbate peroxidase (APX) and catalase (CAT) activities. Metabolic profiling revealed that BQ1 uniquely accumulates carbon-based osmolytes, specifically sucrose and maltose, which correlate with increased levels of Krebs cycle intermediates such as malate and aspartate. While certain unique adaptative responses in BQ1 reached a threshold at high salinity, its growth performance remained markedly superior to the other cultivars, suggesting a highly robust mechanism for sustaining metabolic flux and cellular homeostasis under extreme ionic and osmotic constraints.