Journal of Energy Bioscience 2025, Vol.16, No.3, 139-150 http://bioscipublisher.com/index.php/jeb 142 4 Biofortification Strategies for Wheat 4.1 Agronomic biofortification 4.1.1 Iron fertilizers (soil and foliar) Agronomic biofortification mainly relies on the application of iron fertilizers, such as ferrous sulfate, iron chelates, and nano-iron fertilizers. Foliar iron fertilizer spraying wheat can increase the iron content in the grain, with an average increase of 18.2%. Direct application to the soil is also effective, with an increase of about 26.7% (Zhou et al., 2024). Before the wheat blooms, if more sprays are made and the concentration is slightly higher (for example, more than 0.1%), the effect will be better. If 1% ferrous sulfate and urea are sprayed on the leaves together, the iron content in the grain can reach up to 50 mg/kg, which is a very effective method (Ramzan et al., 2020; Taskın and Gunes, 2022). Soaking seeds with iron nanoparticles can also promote better wheat growth and more iron accumulation (Sundaria et al., 2019; Zulfiqar et al., 2020). 4.1.2 Role of chelators and plant growth conditions Iron chelators, such as Fe-EDDHA, can make iron in the soil more easily absorbed by plants (Taskın and Gunes, 2022). The method of retaining the surface and not tilling the soil, such as "zero tillage", can increase the organic matter and microorganisms in the soil, and indirectly help wheat absorb iron (Zulfiqar et al., 2020). If zinc and iron are sprayed at the same time (such as 0.5% zinc sulfate plus 1% ferrous sulfate), not only can the yield be increased, but the quality of the grain will also be better (Ramzan et al., 2020). 4.2 Conventional breeding 4.2.1 Screening of landraces and wild relatives Conventional breeding is to select local wheat varieties with high iron content or its "wild relatives", and then slowly cultivate new varieties with high iron content. In countries like India and Pakistan, more than 40 high-iron wheat varieties have been promoted through this method (Gupta et al., 2024). At present, there are not many high-quality high-iron gene resources, which also limits the further development of conventional breeding in this regard (Ludwig and Slamet-Loedin, 2019; Tanin et al., 2024). 4.2.2 QTL mapping and marker-assisted selection Molecular breeding techniques, such as QTL positioning, Meta-QTL analysis and GWAS research, have been used to study the genetic basis of wheat iron content. These methods also help scientists find genes related to "high iron" more quickly (Ludwig and Slamet-Loedin, 2019; Tanin et al., 2024). Through molecular marker-assisted selection (MAS), these good genes can be combined more quickly to cultivate a new generation of high-iron wheat (Ali and Borrill, 2020; Tanin et al., 2024) (Figure 2). 4.3 Transgenic approaches 4.3.1 Overexpression of ferritin genes (soybean, rice) Some methods add ferritin genes from other plants, such as soybeans or rice, into wheat. This method can significantly increase the iron content in the grain (Ludwig and Slamet-Loedin, 2019; Tanin et al., 2024). There have been successful cases in rice, and wheat can also learn from this method (Ludwig and Slamet-Loedin, 2019). 4.3.2 Manipulation of NAAT and NAS genes Another way is to regulate the genes responsible for iron transport in wheat itself, such as NAAT and NAS. This allows wheat to absorb and accumulate more iron, and the iron content in the grain will also increase (Ludwig and Slamet-Loedin, 2019; Tanin et al., 2024). 4.4 Gene editing (CRISPR/Cas9): Targeted modifications for iron accumulation Gene editing tools such as CRISPR/Cas9 can accurately "cut and modify" key genes in wheat, such as those that control iron absorption, transportation, and storage. It does not require the introduction of foreign genes to turn wheat into a "new high-iron variety". It is a very promising method and is more easily accepted by the public (Ludwig and Slamet-Loedin, 2019; Tanin et al., 2024).
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