Abstract
Salt stress significantly limits wheat production worldwide, jeopardizing food security and sustainable agriculture. Developing strategies to enhance wheat's resilience to salinity is critical for maintaining yield in affected regions. This study investigates the potential of chitosan-proline (Cs-Pro) and chitosan-glycine (Cs-Gly) nanoparticles in mitigating salt stress in salt-tolerant Heydari and salt-sensitive Sepahan wheat cultivars, with a special question on genotype-dependent differences. Plants were treated with nanoparticles at concentrations of 0, 200, and 400 mg L⁻¹ under salt stress levels of 0, 200, and 400 mM NaCl. The salt-tolerant Heydari cultivar exhibited superior adaptability to saline conditions, in addition reacted more positively to nanoparticle treatments. Results demonstrated significant physiological improvements, including increased relative water content (RWC), enhanced chlorophyll content and elevated proline levels, especially after 400 mg L⁻¹ Cs-Pro treatment. Oxidative stress markers, such as malondialdehyde (MDA) and hydrogen peroxide, were substantially reduced, while antioxidant enzyme activity was boosted. Certain stress-responsive genes (e.g., TaADC, TaPxPAO, TaSAMDC, TaSPDS, TaSOS1, TaNHX1) were upregulated, highlighting the importance of ionic balance and polyamine metabolism in improved stress tolerance. The application of Cs-Pro and Cs-Gly nanoparticles presents a promising approach to enhance wheat's salinity tolerance by improving physiological, biochemical, and molecular responses.