Application of biochar and seed priming with zinc-oxide nanoparticles for enhancing salinity tolerance in wheat (Triticum aestivumL.).

Soil salinity presents a significant nutritional challenge, characterized by high sodium (Na+) levels, which hamper agricultural productivity. Zinc oxide nanoparticles (ZnO NPs) and biochar have gained attention as sustainable methods to mitigate abiotic stresses. However, there is limited information on using ZnO NPs combined with biochar to reduce salinity stress across different salinity levels ((i) non-saline, (ii) slightly saline, (iii) moderately saline, and (iv) highly saline). This study investigated the effects of applying biochar (1.3 w w-1in soil) and ZnO NPs (priming at 50 mg l-1and 100 mg l-1) alone and combined on the growth and nutrient availability of wheat genotypes (V1; Gohar and V2; Van) under salinity stress. Results showed that in the absence of amendments, plants experienced maximum growth retardation under slight to high salinity due to ionic, osmotic and oxidative stress, leading to reduced growth parameters (root and shoot lengths), biomass (fresh and dry weight), photosynthetic rate (via CCI analysis) and lower nutrient availability (K+), increased Na+/K+ratio and affected stress tolerance indices (STI). Application of biochar and ZnO NPs priming improved growth, biomass (fresh and dry weight), chlorophyll content, increased K+and decreased the Na+/K+ratio, enhancing the STI of wheat genotypes (V1; Gohar and V2; Van) under salinity stress. Notably, the combined treatment of ZnO NPs with biochar has a more pronounced beneficial effect. Overall, both individual and combined applications of ZnO NPs and biochar proved effective and sustainable strategies to alleviate salinity stress and enhance crop growth quality.