Soil and foliar selenium application: Impact on accumulation, speciation, and bioaccessibility of selenium in wheat (Triticum aestivum L.)

Abstract

A comprehensive study in selenium (Se) biofortification of staple food is vital for the prevention of Se-deficiency-related diseases in human beings. Thus, the roles of exogenous Se species, application methods and rates, and wheat growth stages were investigated on Se accumulation in different parts of wheat plant, and on Se speciation and bioaccessibility in whole wheat and white all-purpose flours. Soil Se application at 2 mg kg–1 increased grains yield by 6% compared to control (no Se), while no significant effects on yield were observed with foliar Se treatments. Foliar and soil Se application of either selenate or selenite significantly increased the Se content in different parts of wheat, while selenate had higher bioavailability than selenite in the soil. Regardless of Se application methods, the Se content of the first node was always higher than the first internode. Selenomethionine (SeMet; 87–96%) and selenocystine (SeCys2; 4–13%) were the main Se species identified in grains of wheat. The percentage of SeMet increased by 6% in soil with applied selenite and selenate treatments at 0.5 mg kg–1 and decreased by 12% compared with soil applied selenite and selenate at 2 mg kg–1, respectively. In addition, flour processing resulted in losses of Se; the losses were 12–68% in white all-purpose flour compared with whole wheat flour. The Se bioaccessibility in whole wheat and white all-purpose flours for all Se treatments ranged from 6 to 38%. In summary, foliar application of 5 mg L–1 Se(IV) produced wheat grains that when grounds into whole wheat flour, was the most efficient strategy in producing Se-biofortified wheat. This study provides an important reference for the future development of high-quality and efficient Se-enriched wheat and wheat flour processing.

Direct and indirect selenium speciation in biofortified wheat: A tale of two techniques

“…The fact that the translocation of inorganic Se to the reproductive organs is minimal is advantageous to produce fortified food products since inorganic Se is more toxic than its organic counterparts (Rayman et al, 2008 ). These findings agree with previous studies on wheat, even though our conditions led to lower amounts of inorganic Se and a higher percentage of SeCyst (Di et al, 2023 ; Wang et al, 2022 ; Wang, Ali, et al, 2020 ).…”

“…Selenate is also commonly quantified, with literature reporting values below 5% (Galinha et al, 2015;Warburton & Goenaga-Infante, 2007). An extremely limited number of studies have achieved a successful determination of the five Se species (Di et al, 2023;Eiche et al, 2015;Hart et al, 2011;Wang et al, 2022;Wang, Ali, et al, 2020;Xiao et al, 2021), and the present study is the first to quantify six species in wheat. Likewise, very few have used complementary techniques to confirm species identification and validate the applied method (Aureli et al, 2012;Warburton & Goenaga-Infante, 2007).…”

Characterization of Selenium Speciation in Se-Enriched Crops: Crop Selection Approach

“…This study is consistent with the findings of previous studies, which emphasize that SeMet is generally the principal organic species found in Se-enriched staple crops. For example, wheat can store 87–96% of SeMet and 4–13% SeCys 2 in the grains as an edible part, regardless of the application rate of exogenous Se . Similarly, SeMet was extracted in wheat (∼90%) and about 65–87% of total extractable Se species in Se-enriched wheat flour and bread .…”

“…The main form of fertilized-derived Se in grains was SeMet with an abundance of ∼92% in Zea mays L., ∼63% in cowpea, and ∼85.2% in groundnuts . Wang et al revealed in a recent study that SeMet (∼96%) and SeCys 2 (∼8%) were the main Se forms identified in grains of wheat, and inorganic Se accumulation of Se­(VI) was found in wheat leaves. The predominant organic form in garlic is SeMeCys (with anticarcinogenic properties), and similarly onion contained SeMeCys as a major forms, while major organic and inorganic forms in broccoli were SeMeCys, Se­(IV) and Se­(VI) …”

“…For example, wheat can store 87−96% of SeMet and 4−13% SeCys 2 in the grains as an edible part, regardless of the application rate of exogenous Se. 20 Similarly, SeMet was extracted in wheat (∼90%) 21 and about 65−87% of total extractable Se species in Se-enriched wheat flour and bread. 22 Moreover, Muleya et al 15 found an abundance of organic Se species (61−64%) in maize while Se-enriched rice contained SeMet (92.0%) and ∼84% of seleniferous soils.…”