Recently, it appears that the utilization of some soil microorganisms such as arbuscular mycorrhizal (AM) fungi and plant growth promoting rhizobacteria (PGPR) as an environmentally-friendly and sustainable strategy, as an alternative to current agricultural practices, can play an important role in preventing Fe-deficiency. To the best of our knowledge, there are no published reports concerning the effects of AM fungi and PGPR on Fe acquisition in quince seedlings under Fe deficiency condition. Therefore, this study was designed in two separate experiments to investigate the potential of AM fungi and PGPR to improve quince seedling Fe content and to gain an understanding of not only the physiological and biochemical mechanisms facilitating Fe uptake, but also the genes, under direct Fe-deficiency (The first experiment) and indirect Fe deficiency conditions (The second experiment). The first experiment was divided into two parts. The first part was arranged as a factorial experiment with two factors, including AM fungi inoculation treatments (non-AM, Funneliformis mosseae , Rhizophagus intraradices and combination of both fungi), and PGPRinoculation regimes ( Pseudomonas fluorescens , Microcuccuce yunnanensis and combination of both PGPR) as the first main factor and two Fe levels (50 µM representing Fe-sufficiency and 5 µM as Fe-deficiency) as the second factor. Theecondartoftheexperiment,which evaluated the role of AM fungi and PGPR on the expression of genes, was included AM fungi and PGPR treatments, applied separately, and two Fe levels (50 µM and 5 µM). For expression of genes, lateral roots were sampled at 0, 2, and 7 days after the start of Fe-deficiency treatments. The second experiment was arranged as a factorial experiment with two factors. The first factor was similar to the first experiment and the second factor was included four levels of sodium bicarbonate (0, 5, 10, and 15 mM NaHCO 3 ) with pH 5.5, 6.5, 7.5, and 7.8, respectively. The results showed that Fe-deficiency increased root colonization (The first experiment), but increasing the concentration of sodium bicarbonate in the nutrient solution decreased root colonization (The second experiment). In both experiments, the percentage of root colonization was significantly higher in seedlings inoculated with R . intraradices than in those inoculated with F. mosseae . Under both direct and indirect Fe deficiency, the vegetative traits, leaf chlorophyll and carotenoids content, chlorophyll fluorescence, soluble carbohydrates content, and leaf antioxidant enzyme significantly reduced compared to the Fe-sufficiency condition, whereas seedlings treated with AM and PGPR showed less decrease in all measured parameters. The leaf hydrogen peroxide and malondialdehyde content increased under both Fe deficiency conditions compared to the Fe-sufficiency. However, quince seedlings treated with AM and PGPR had a significantly lower leaf hydrogen peroxide and malondialdehyde content than that of non-treated plants. Under all Fe deficiency conditions, R. intraradices , both PGPR treatments especially M. yunnanensis , and the combination of two PGPR increased activity of root ferric chelate reductase and phenylalanine ammonia-lyase as well as total root phenolic compounds in comparison with non-treated plants. In AM and PGPR treated plants, HA 7 gene expression was found correlated with root growth characteristics. In addition, the AM and PGPR treatments significantly increased the expression of PAL 1 , FRO 2 , and CS 1 genes compared with non-treated plants under Fe deficiency condition, in parallel with the increase in the phenylalanine ammonia-lyase and root ferric chelate reductase activities; and citric acid accumulation. In both experiments, in AM and PGPR treated plants, root and leaf Fe concentrations were significantly higher than the non-treated plants. The overexpression of Fe traorter ( IRT 1 ) gene in AM and PGPR treated plants compared to the non-treated Overall, the results showed that quince seedlings are not able to activate mechanisms to overcome Fe deficiency. In contrast, AM and PGPR treatments especially, R. intraradices , M. yunnanensis and the combination of both PGPR played a key role in improving Fe deficiency by influencing physiological, biochemical, and molecular responses. Key Words Antioxidant enzymes, Beneficial microorganisms, Bio-stimulants, Ferric chelate reductase, Phenolic compounds, Phenylalanine ammonia-lyase, Sodium bicarbonate, Fe deficiency