This study aims to investigate the expression of the nifX gene under the influence of bacterial inoculation and molybdenum application in selected cultivars of broad bean (Vicia faba L.),
A field study was conducted in the winter season of 2023–2024 in the research fields of Baghdad University to evaluate the effect of Rhizobium leguminosarum inoculation and foliar application of molybdenum (Mo) on the root characteristics and expression of the nitrogen-fixing nifX gene in on broad bean (Vicia faba L.) cultivars. The experiment was laid out in a randomized complete block design (RCBD) in a split-split plot arrangement with three replications, that included bacterial inoculation (Bo: control, no inoculation; B₁: 2 × 10⁸ CFU mL⁻¹), molybdenum concentrations (M₀: 0 mg L⁻¹, M₁: 5 mg L⁻¹, M₂: 10 mg L⁻¹), and three broad bean cultivars (V₁: Hannaoui, V₂: Spanish, V₃: Loz). The results revealed an inverse relationship between CT values and gene expression, where both bacterial inoculation and molybdenum application enhanced nifX gene expression. The highest nifX expression levels were observed in treatments V1B1 M2, V2B1M1, and V₃B₁M₁, with the Hannaoui cultivar exhibiting peak expression at 10 mg L⁻¹ Mo, while Spanish and Loz cultivars performed optimally at 5 mg L⁻¹ Mo. Notably, the V₁M₁B₁ treatment recorded the highest active nodule count (845 nodules plant⁻¹) and root dry weight (48.935 g), highlighting the synergistic role of Rhizobium inoculation and Mo supplementation in improving nitrogen fixation efficiency and root growth traits in broad bean