Foliar application of chitosan-silicon nanoparticles and salicylic acid enhances salinity tolerance and yield of common bean (Phaseolus vulgaris L.) under field conditions

BACKGROUND: Salinity stress restricts the growth and productivity of common bean (Phaseolus vulgaris L.), a salt-sensitive legume. This study evaluated the foliar application of nanoparticle (NP) formulations to alleviate salt stress under moderate soil salinity (EC 7.71-7.83 dS m⁻¹). A two-season field experiment tested foliar sprays with salicylic acid (SA), silicon nanoparticles (Si-NPs), chitosan nanoparticles (Ch-NPs), chitosan-silicon nanoparticles [Ch-Si (NPs)], and Ch-Si (NPs) + SA. Growth parameters, photosynthetic pigments, gas exchange, oxidative stress markers, antioxidant enzyme activities, osmoprotectants, nutrient content, and pod yield were measured. RESULTS: Salinity stress reduced plant growth, photosynthetic efficiency, and nutrient balance while increasing oxidative damage. All treatments mitigated these effects, with Ch-Si (NPs) + SA showing the greatest improvement. Compared with the saline control, this treatment increased shoot dry weight and green pod yield by approximately twofold and enhanced net photosynthetic rate by about 40%. Leaf K⁺/Na⁺ ratios increased by 113.9%-126.3%, while Na⁺ content decreased by 37.2%-39.9%, electrolyte leakage by 44.7%-46.7%, and malondialdehyde by 55.8%-59.0% across both seasons. Ch-Si (NPs) + SA also increased activities of enzymatic antioxidants (catalase, peroxidase, ascorbate peroxidase, superoxide dismutase, glutathione reductase) and levels of non-enzymatic antioxidants (proline, ascorbate, glutathione, α-tocopherol) compared with the control. CONCLUSIONS: Foliar application of Ch-Si (NPs) + SA was associated with improved physiological performance, oxidative balance, and yield of common bean grown under saline field conditions. This combination may offer a promising biostimulant strategy for legume production in salt-affected soils, though further research is needed to establish broader applicability and long-term effects.