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Abstract

This study was conducted at National Institute for Genomics and Advanced Biotechnology (NIGAB), National Agricultural Research Centre (NARC), Islamabad, Pakistan, during 2015–2016 cropping season. The objectives were to evaluate physiological, biochemical, and growth responses of wheat genotypes under salt stress, and to assess their genetic diversity using SSR and RAPD markers. In germination experiments, cultivars were tested against 50, 75, 100, 125 and 150 mM salt levels. The research novelty lies in the integrative approach combining morphological, physiological, biochemical, and molecular characterization to identify salt-tolerant wheat genotypes suitable for breeding programs, which has not been extensively reported for these locally important cultivars. A completely randomized design (CRD) with three replications was used for both germination and hydroponics experiments. Salt stress significantly affected seed germination and seedling growth of the four wheat genotypes. At 150 mM NaCl, germination reduction was lowest in Local White (20–30%) and Pasban-90 (30–40%) and highest in Frontana (50–60%) and Chakwal-97 (40%). Similarly, total chlorophyll content was decreased by 23% and 26% in Local White and Pasban-90, respectively, while Chakwal-97 and Frontana showed higher reductions of 36% and 37%. These results showed that Local White and Pasban-90 exhibited comparatively higher tolerance to salt stress. Under 150 mM salt stress, wheat genotypes Local White and Pasban-90 exhibited higher tolerance compared to Chakwal-97 and Frontana. Seedling shoot length was reduced by 20% and 35% in Local White and Pasban-90, respectively, while Chakwal-97 and Frontana showed reductions of 41% and 46%. Root length was declined by 30–31% in tolerant genotypes versus 38–46% in sensitive ones. Fresh weight was decreased by 26% in Local White and Pasban-90 but by 46–49% in Chakwal-97 and Frontana, whereas dry weight reductions were <20% in tolerant and >30% in sensitive genotypes. Physiologically, total chlorophyll content was decreased by 23–26% in tolerant genotypes and 36–37% in sensitive ones; chlorophyll a and b showed similar trends. Relative water content, membrane stability index, water potential, and osmotic potential were minimally affected in Local White and Pasban-90 (reductions 23–30%) but markedly decreased in Chakwal-97 and Frontana (reductions 40–52%). SSR based genetic diversity study showed that these genotypes were genetically divergent. These results demonstrate a strong association between physiological resilience and molecular divergence, supporting the selection of Local White and Pasban-90 as promising parents for salt-tolerance breeding programs.

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