Rhizoglomus clarum inoculation enhances drought tolerance and photosynthetic performance of maize in sterile and natural soils

Drought is a major constraint on maize production worldwide, particularly in tropical regions where climate variability is intensifying. Arbuscular mycorrhizal fungi (AMF) have emerged as beneficial symbionts enhancing plant resilience to drought by improving water uptake, nutrient acquisition, and photosynthetic performance. This study evaluated the effects of Rhizoglomus clarum inoculation on maize growth, water status, osmotic adjustment, and chlorophyll a fluorescence under well-watered (WW) and water-deficit (WD) conditions in sterile and natural soils. The experiment was conducted in a greenhouse using a randomized complete block design in a 4 × 2 factorial scheme (soil treatment × water regime), with four replicates. Drought significantly reduced leaf area, shoot and root biomass, and water status. However, R. clarum inoculation attenuated these effects, increasing leaf dry mass by up to 45% and stem dry mass by 100% in under WD. Inoculated plants also showed higher photochemical efficiency (Fv/Fm and PI _ABS ) under both water regimes. The strongest responses were observed in natural soil, suggesting synergistic interactions between R. clarum and indigenous microbiota. These results demonstrate that R. clarum enhances maize drought tolerance through coordinated morphological, physiological, and photochemical adjustments. This highlights the potential of species-specific AMF inoculation as a sustainable strategy to improve maize performance under water-limited conditions.