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Introduction
Iron is an essential nutrient in the life cycle of all organisms. Inadequate dietary intake of Fe has greatly contributed to the prevalence of Fe deficiency in humans (Connorton and Balk 2019). Increasing Fe concentration and bioavailability in food crops is an important challenge as about two billion people globally have Fe deficiency, especially in the regions where staple foods are based on cereal crops such as wheat. Biofortification is a word that means enrichment of the nutritional quality of food crops through agronomic practices, and wheat is an ideal crop for biofortification because it is the main cereal crop worldwide which is responsible for about 50% of the daily calorie intake and also basic dietary source proteins and micronutrients in many of the developing countries (Finkelstein et al. 2017; WHO 2017).
Iron deficiency in plants, animals and humans is a widespread nutritional disorder. Although total Fe content in soils is usually high, the available Fe in soil for plants is often insufficient, particularly in calcareous soils, due to low solubility of Fe (Sharma et al. 2019). Cereals are in the strategy II group in terms of Fe nutrition. In practice, there is no problem with Fe nutrition in cereals. Because phytosiderophores secreted by strategy II plants form a chelate with Fe3+ ions in the rhizosphere and this chelate complex is transported to the cytoplasm by passing through channels in the plasma membrane with the help of special transporters (Marschner 2012). In addition to this, the main problem is that the transport of Fe to grains via phloem is limited (Garnett and Graham 2005). For this reason, increasing the Fe content of grain is an important and priority issue for human health. Hence, the application of various ferrous fertilizers to the upper parts of the plant during appropriate development periods can be an effective strategy.
It is important to improve the utilization efficiency of Fe fertilizers. Chelated and inorganic forms of different Fe sources such as FeSO4, FeEDTA, FeDTPA, FeEDDHA and Fe-citrate can be used to eliminate Fe deficiency in plants and also biofortification. The chelate forms among them are very effective for soil application, but it is not effective in foliar application due to its large molecular structure. In this...