Increasing soil salinity due to global warming severely restricts crop growth and yield. To select and recommend salt-tolerant cultivars, extensive genotypic screening and examination of plants’ morpho-physiological responses to salt stress are required. In this study, 18 prescreened maize hybrid cultivars were examined at the early growth stage under a hydroponic system using multivariate analysis to demonstrate the genotypic and phenotypic variations of the selected cultivars under salt stress. The seedlings of all maize cultivars were evaluated with two salt levels: control (without NaCl) and salt stress (12 dS m⁻¹ simulated with NaCl) for 28 d. A total of 18 morpho-physiological and ion accumulation traits were dissected using multivariate analysis, and salt tolerance index (STI) values of the examined traits were evaluated for grouping of cultivars into salt-tolerant and -sensitive groups. Salt stress significantly declined all measured traits except root–shoot ratio (RSR), while the cultivars responded differently. The cultivars were grouped into three clusters and the cultivars in Cluster-1 such as Prabhat, UniGreen NK41, Bisco 51, UniGreen UB100, Bharati 981 and Star Beej 7Star exhibited salt tolerance to a greater extent, accounting for higher STI in comparison to other cultivars grouped in Cluster-2 and Cluster-3. The high heritability (h²_bs, >60%) and genetic advance (GAM, >20%) were recorded in 13 measured traits, indicating considerable genetic variations present in these traits. Therefore, using multivariate analysis based on the measured traits, six hybrid maize cultivars were selected as salt-tolerant and some traits such as Total Fresh Weight (TFW), Total Dry Weight (TDW), Total Na⁺, Total K⁺ contents and K⁺–Na⁺ Ratio could be effectively used for the selection criteria evaluating salt-tolerant maize genotypes at the early seedling stage.

Comparative physiological analysis was performed to understand the differences in the mechanisms of salinity tolerance in two rice (Oryza sativa L.) cultivars (the tolerant cultivar CFX18 and the susceptible cultivar Juma67). It was found that growth was significantly decreased in Juma67, but not in CFX18, during 10 d of salinity treatment. Under high salinity conditions, CFX18 maintained a better physiological status as determined by higher leaf water potential and a lower electrolyte leakage ratio compared to Juma67. Analysis of photosynthesis-intercellular carbon dioxide (CO₂) concentration response curves revealed decreases in both carboxylation efficiency and maximum photosynthetic CO₂ fixation rate in Juma67 in response to salinity stress, suggesting reduced photosynthetic capacity in this cultivar. In addition, it was observed that under high salinity conditions, Juma67 accumulated 3.5 times more sodium ions (Na⁺) in the leaves compared to CFX18. To corroborate this observation, quantitative expression analysis was conducted to examine changes in the transcript levels of OsHKT1;5, which is responsible for the regulation of Na⁺ accumulation in shoots. It was found that salinity stress repressed expression of the OsHKT1;5 gene in the leaves of Juma67, but not CFX18. These results suggest that CFX18 and Juma67 differ in their profiles of Na⁺ accumulation under salinity stress because of differences in OsHKT1;5 expression. Thus, the mechanism of salinity tolerance seen in CFX18 relies on regulating Na⁺ accumulation in leaves and this trait would be useful for improving salinity tolerance in rice.