Interaction Effects of Arbuscular Mycorrhizal Fungi and Iron-Copper Nanoparticles on Inducing Drought Stress Tolerance in Bread Wheat (Triticum aestivum L.)

Drought stress is one of the most critical environmental constraints affecting wheat production worldwide. This two-year field study (2022–2024) investigated the interactive effects of arbuscular mycorrhizal fungi (AMF) inoculation and foliar application of iron-copper nanoparticle mixture on inducing drought tolerance in bread wheat (Triticum aestivum L. cv. Parsi). A factorial experiment based on randomized complete block design with three replications was conducted at the Agricultural Research Station in a semi-arid region. Experimental factors included irrigation regimes at two levels (normal irrigation at 80% field capacity and drought stress at 50% field capacity from stem elongation to grain filling stages), AMF inoculation at two levels (with and without Funneliformis mosseae at 120 spores/g soil), and foliar application of Fe3O4–CuO nanoparticle mixture at three concentrations (0, 50, and 100 ppm). Results demonstrated significant three-way interactions among all factors (irrigation regime, AMF inoculation, and nanoparticle concentration) for most of the 30 measured agronomic and physiological traits across both experimental years. Under drought stress, the combined application of AMF inoculation with 100 ppm nanoparticles significantly improved grain yield by 43.5% in Year 1 and 47.6% in Year 2, relative water content by 30.9% and 33.0%, chlorophyll content by 33.8% and 35.3%, and photosynthetic rate by 45.9% and 49.6% compared to non-inoculated controls. Multiple regression analysis identified photosynthetic rate, relative water content, chlorophyll content, and MDA as the strongest predictors of grain yield (R2 = 0.94). Path analysis revealed that AMF and nanoparticles exerted both direct effects on yield and indirect effects mediated through improved water relations and antioxidant defense. GGE biplot analysis confirmed superior performance and stability of the combined treatment across environments. These findings demonstrate that integrating biological and nanotechnological approaches synergistically mitigates drought-induced yield losses in wheat through complementary physiological mechanisms.