Cumin is one of the most popular herbs that is used widely as a spice and medicinal purposes. In Iran, cumin is mainly cultivated in high pH soils in arid regions where some elements such as iron (Fe) and zinc (Zn) cannot be adequately absorbed. Accordingly, we hypothesized that using chelating agents like bacterial siderophore could alleviate nutrient deficiency under such conditions. Cumin ecotypes (Sabzevar, Torbat-e-Jam, Taibad, and Shiraz) and bacterial siderophore treatments (control, seed priming, foliar spray, and seed priming + foliar spray (combined); 0.2%) were considered as the experimental factors. The application of siderophore increased the concentration of Fe, Zn, and nitrogen (N) in leaves and grains compared with the control. The highest leaf Fe concentration was observed when the combined treatment was applied. Sabzevar showed the highest grain Fe and Zn concentrations by 110 and 50%, respectively, over the control in the combined treatment. The highest grain yield was obtained from the combined-treated Taibad plants by a 28% increase over the control. Compared with the control, essential oil yield was increased by 22% in the combined-treated plants. The results showed that the combined application of siderophore had a higher efficiency among the other treatments. Furthermore, bacterial siderophore could be usefully applied to improve physiological traits, nutrient absorption, and grain yield in cumin under an arid region.

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