Unraveling salinity stress tolerance: Contrasting morpho-physiological, biochemical, and ionic responses in diverse...

Salinity stress poses a significant threat to crop production due to rapid soil salinization as a consequence of climate change. Brinjal, a vital and resilient vegetable crop with extensive genetic variation, exhibits a diverse range of salt tolerance responses. Salt-tolerant and susceptible brinjal genotypes were assessed for their differential tolerance mechanisms under 8 dS m^-1 salinity. The results indicated that susceptible genotypes experienced greater reductions in growth, attributing to their lower chlorophyll content, poor photosynthesis, higher lipid peroxidation (MDA), and reduced antioxidant enzyme activity. In contrast, the tolerant genotypes maintained better photosynthesis and antioxidant enzyme activity under salinity stress. Further observations revealed that tolerant genotypes regulated the uptake and translocation of Na⁺ and Cl^- ions into leaves, suggesting the presence of root-level ion exclusion and retention mechanisms, without hampering beneficial ion (K⁺, Ca²⁺ and Mg²⁺) uptake. Principal component analysis, showed that genotypes IIHR-766, IIHR-832 and IIHR-766-A were highly salt-tolerant, whereas Utkal Anushree, Sharapova Bottle Brinjal, and S. gilo were highly salt-sensitive. Additionally, cluster analysis indicated that antioxidant enzymes, along with leaf Ca²⁺ and Mg²⁺ prominently contributed to salt-tolerance, while MDA, Na⁺, Cl^- and Na⁺/K⁺ ratio imparted sensitivity. Correlation analysis revealed a positive association of photosynthetic parameters with leaf Ca²⁺ and canopy temperature with leaf Na⁺ and Na⁺/K⁺ ratio. However, antioxidant enzymes correlated negatively with leaf Na⁺ and Cl^- and positively with leaf and root Ca²⁺ and Mg²⁺, whereas MDA exhibited an inverse relationship to these patterns. In conclusion, the present study identifies the salt tolerance mechanisms existing in highly salt-tolerant brinjal genotypes and elucidates the influence of differential ion accumulation on these traits.