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Article

Selenium Application Provides Nutritional and Metabolic Benefits to Wheat Plants

by
Túlio Silva Lara
1,
Tatiane Santos Correia
2,
Cynthia de Oliveira
3,
Josimar Henrique de Lima Lessa
3,
Kamila Rezende Dázio de Souza
4,
Ana Paula Branco Corguinha
3,
Ediu Carlos da Silva, Jr.
3,
Fábio Aurélio Dias Martins
5,
Guilherme Lopes
3 and
Luiz Roberto Guimarães Guilherme
3,*
1
Institute of Sciences and Water Technology, Federal University of West of Pará, Santarém 68040-470, PA, Brazil
2
Institute of Sciences Natural, Federal University of Lavras, Lavras 37203-202, MG, Brazil
3
Department of Soil Science, Federal University of Lavras, Lavras 37203-202, MG, Brazil
4
Institute of Natural Sciences, Federal University of Alfenas, Alfenas 37130-001, MG, Brazil
5
State of Minas Gerais Agricultural Research Corporation, Epamig, Lavras 37200-900, MG, Brazil
*
Author to whom correspondence should be addressed.
Agronomy 2024, 14(3), 462; https://doi.org/10.3390/agronomy14030462
Submission received: 25 October 2023 / Revised: 28 November 2023 / Accepted: 31 January 2024 / Published: 26 February 2024
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Abstract

:
Selenium is beneficial to plants and is essential for animals and humans, which justifies any efforts for producing Se-enriched wheat grains worldwide. This study aimed to (i) verify if wheat is an efficient species to be used for Se biofortification in tropical agroecosystems and (ii) assess the influence of Se on the physiological and biochemical parameters of wheat plants. Selenium was applied as sodium selenate (Na2SeO4) at different doses (12, 21, 38, 68, and 120 g ha−1) in soil. The dose of 120 g ha−1 of Se resulted in Se contents of 7.98 and 2.27 mg kg−1 in the leaves and grains, respectively. The supply of 38 g ha−1 of Se increased the total soluble sugar content by 50%, with reducing sugars increasing by 17% and sucrose augmenting 53%, compared with that in the control. The doses of 12, 68, and 120 g of Se ha−1 promoted a significant increase in catalase activity. In addition, Se application increased carbohydrate and nutrient contents. Our findings indicate that wheat is a good species for agronomic biofortification with Se via soil application in tropical agroecosystems. Selenium proved to be a valuable element for plants since it provides physiological and biochemical benefits.

1. Introduction

Selenium (Se) is a beneficial element to plants and an important micronutrient for humans and animals since it is a component of 30 selenoproteins, such as glutathione peroxidase, thioredoxin reductase, and iodothyronine deiodinase [1]. These enzymes are related to protection mechanisms against oxidative stress, the maintenance of redox and immune status, as well as to thyroid hormone and anti-inflammatory functions [2]. Due to its essentiality, a daily intake of 60 and 70 µg Se day−1 is recommended for adult women and men, respectively [3]. Not only deficiency but also an excess of Se can also cause disorders in human and animal health. However, this excess is rare (i.e., a Se intake > 400 μg day−1), this being much less worrying in the world than the lack of this element (a Se intake < 40 μg day−1) [4].
Nevertheless, it is estimated that one billion people around the world are Se-deficient [5] and biofortification (genetic or agronomic) is a good approach to enhance Se content in edible parts of staple crops and, consequently, its levels in humans and animals [6]. Agronomic biofortification with Se is reached through practices such as soil fertilization, aiming to increase soil Se contents and making the nutrient available to be absorbed and assimilated by plants, therefore letting it be included in the diets of humans and animals [7]. Biofortification is a proper and secure way to enrich plants with Se, allowing for better-quality food products in terms of safety and quality [5].
Agronomic biofortification has been applied to wheat, which is the second most cultivated cereal crop worldwide [8] and an important basic material to produce bread, pasta, flour, and cakes [9]. Despite not being a Se-accumulating plant, wheat can have its Se levels increased significantly in its grains and leaves after soil and/or foliar Se applications [10].
Selenium supplementation has been described as beneficial to plants, increasing the growth and yield of some species, including wheat [11], which is a Se-sensitive crop with strong Se enrichment ability [12]. However, the mechanisms by which Se promotes these benefits have not been fully understood yet [13]. The addition of Se in basic fertilization (NPK) can attenuate the effects caused by abiotic stresses [14]. Selenium’s benefits can be related to its performance in the maintenance of cellular homeostasis, due to a higher antioxidant capacity and decreased oxidative stress [15]. Additionally, Se plays an important role in regulating the activity of carbohydrates and nitrogen metabolism enzymes, increasing the photosynthetic rate and the efficiency of the photosystem II photochemical step, which leads to higher plant growth [11,13].
Few studies have addressed the efficiency of Se biofortification in wheat and its influence on the contents of major carbohydrates in plants under field conditions in tropical agroecosystems. Given that, this study aimed to (i) verify the efficiency of wheat as a crop for Se biofortification under tropical soil and climate conditions and (ii) assess the influence of Se on carbohydrate metabolism, phosphorus (P), nitrogen (N), and sulfur (S) accumulation and antioxidant system activity, as well as the chlorophyll index in wheat plants. These results can indicate if Se application in wheat plants can alleviate Se deficiency in humans and animals while, at the same time, aggregating value to the harvested product.

2. Materials and Methods

2.1. Experimental Design

The experiment was conducted during the cropping winter season of 2015 at the experimental station of the Minas Gerais Agricultural Research Company (EPAMIG), located in Lambari, State of Minas Gerais, Brazil. Se availability is influenced by a variety of soil physicochemical characteristics, redox conditions, and competing anions, such as sulfur and phosphorus, in addition to the high pH, which promotes the release of Se from soil particles, and OM, which alters the soil microstructure, facilitating the reduction and fixation (immobilization) of Se with the help of microorganisms [15]. To understand this relationship, the physical–chemical attributes of the soil were determined by the method in EMBRAPA [16] and are presented in Table 1.
Liming was applied at a dose of 4 t ha−1 30 days before the sowing, aiming to increase the base saturation to 50%. Basal fertilization was carried out by applying 300 kg ha−1 of a commercial fertilizer, formula NPK 08-28-16. The wheat (Triticum aestivum L.) variety used was BRS 264, which was sowed on 25 May 2015. Thirty days after wheat cultivation, a dose of 170 kg ha−1 of NPK 20-00-20 was applied as a top dressing. For the period in which the crop remained in the field, the total precipitation of the area was 236 mm, with minimum and maximum temperatures of 3 °C and 34 °C, respectively.
Fertilization with Se via the soil was carried out on 30 June 2015, using different doses, 12, 21, 38, 68, and 120 g ha−1, which were defined from previous field studies [11,17]. Sodium selenate (Na2SeO4) was diluted in 2 L of deionized water. The application of the solution containing the doses of Se was performed at 5 cm from the planting line. The solutions were applied using a pressurized pump coupled with a carbon dioxide container, which allowed for a uniform application of the treatments.
The experiment followed a randomized block design, with 4 replications. Plots were five meters long and two meters wide (10 m2), with a row spacing of 0.17 cm, totaling twelve planting rows per plot. The usable area was 5.5 m2 (4 m long by 1.36 m wide), representing eight lines. The control treatment received only 2 L of deionized water. Thus, five treatments plus the control treatment totaled twenty-four experimental plots.

2.2. Physiological and Agronomic Analyses

Analyses of antioxidant enzymes and SPAD readings were used only for the flag leaf, while for the other analyses, the material was derived from the dry mass quantification of the shoot, excluding the existing panicles. Leaf sampling was performed by removing the useful area after 14 days of Se fertilization.

2.2.1. Grain Yield

Grain yield was evaluated in each plot, considering the grain yield of each useful area. The harvest was performed manually, and grain moisture was determined according to the Regulation for Seed Analysis [18].

2.2.2. Quantification of Shoot Biomass and Contents of Carbohydrates, Proteins, and Total Amino Acids

For the quantification of shoot biomass, 6 plants were collected per plot, divided into 2 replicates of 3 plants. The collected materials (i.e., shoots, except for grains) were dried in a forced-air circulation oven at 60 °C until constant weight. Subsequently, the material was weighed using an analytical balance with 0.01 g accuracy. From this material, 0.2 g samples were taken from each treatment to determine the levels of starch and sucrose as well as total soluble sugars (TSSs) [19], reducing sugars (RSs) [20], and total free amino acids [21].

2.2.3. Contents of Selenium, Sulfur, Phosphorus, and Nitrogen

Samples used for the quantification of selenium (Se), sulfur (S), phosphorus (P), and nitrogen (N) in the shoot came from the material used to quantify the shoot biomass, after removing it from the wheat panicles. The sample for the quantification of Se in the grains was collected after assessing the grain yield. The extracts for the quantifications were derived from the acid digestion of 0.5 g for the Se and 0.2 g for the S, N, and P of the material, using digester blocks. For digestion, 6 mL of a 2:1 (v/v) ratio mixture of nitric and perchloric acid were added to the samples, which stood overnight at room temperature, followed by dissolution at 200 °C for 2 h. After complete digestion, 10 mL of distilled water was added to the extracts. Elemental determinations were performed using a graphite furnace atomic absorption spectrophotometer (GF-AAS). To validate the reliability of Se determinations, the procedure was also performed using a certified reference material (BCR®-414 Plankton). Total N content was determined by sulfuric digestion and Kjeldahl distillation [22].
The average Se concentration in the standard reference material (Plankton, BCR®-414) was 1.75 mg kg−1, while the obtained Se value in the analysis was 1.33 mg kg−1, therefore presenting a recovery rate of 76% and confirming the reliability of the data for Se analyses.

2.2.4. Antioxidant Enzymes

The enzymatic extract was obtained by grinding 0.2 g of fresh leaves in liquid nitrogen using an agate mortar and pestle. The enzyme extract was composed of 1.5 mL of extraction buffer containing 0.1 mol L−1 of potassium phosphate buffer (pH 7.8), 0.1 mol L−1 of EDTA (pH 7.0), 0.5 mol L−1 of DTT, 0.1 mol L−1 of PMSF, 0.001 mol L−1 of ascorbic acid, and 22 mg of PVPP. The extract was centrifuged at 14,000× g for 10 min at 4 °C and the supernatant was collected and stored at −20 °C during the analysis period [23]. The collected supernatants were used in the enzymatic analysis of superoxide dismutase (SOD), according to Giannopolitis and Ries [24]; catalase (CAT), according to Havir and McHale [25]; and ascorbate peroxidase (APX), according to Nakano and Asada [26]. Analyses were carried out in triplicates using Elisa-plate spectrometry.

2.2.5. Hydrogen Peroxide (H2O2) and Lipid Peroxidation (MDA)

Hydrogen peroxide was obtained by maceration in liquid nitrogen of 0.2 g of leaves, which were homogenized in 5 mL of trichloroacetic acid (TCA) and centrifuged at 12,000× g for 15 min at 4 °C [27]. Lipid peroxidation was determined by the quantification of malondialdehyde (MDA) [28].

2.2.6. Chlorophyll Index

The chlorophyll index was obtained from the average of five analyses from different plants in each plot, which was performed in the medium portion of the leaf limb, using a portable chlorophyll meter, SPAD-502 (Konica Minolta, Tokyo, Japan). The readings were taken 14 days after fertilization.

2.3. Statistical Analysis

Statistical analyses were performed using the SISVAR program version 5.8.92 [29]; the data were checked for normality (Shapiro–Wilk test) and submitted to analysis of variance using the Scott-Knott test (p < 0.05) for means comparison. Graphics were made using the SigmaPlot Software (version 12.5, Systat Software, Chicago, IL, USA).

3. Results

3.1. Agronomic Wheat Yield

Selenium treatments did not have a significant influence on the grain yield, which ranged from 650 to 800 kg ha−1 (Table S1 of supporting information). Such low yields were caused by the abnormally low temperatures that occurred during the winter season of 2015. However, Se positively influenced the biomass accumulation of wheat plants. Plants that were treated with Se, regardless of the applied doses, presented higher biomass increments when compared with those in the control treatment (Figure 1). The concentrations of N, total amino acids, and total proteins in wheat grain are presented in (Figure S1 of supporting information).

3.2. Selenium Contents of Leaves and Grains

Selenium levels in wheat leaves and grains increased significantly when plants of Triticum aestivum L., variety BRS 264, were subjected to increasing Se doses applied to the soil. The highest concentrations were 2.27 mg kg−1 in grains and 7.98 mg kg−1 in shoots with the application of 120 g ha−1 of Se (Figure 2A,B).

3.3. Contents of Sulfur, Phosphorus, and Nitrogen

In the shoots, the treatments with Se promoted increases in nitrogen (N) and sulfur (S) accumulation, while for phosphorus (P), no statistical difference was observed (Figure 3). However, in the grains, treatments with Se did not induce the accumulation of N, S, and P. The lowest Se dose (i.e., 12 g ha−1) promoted the highest accumulation of N in the shoots, while for the accumulation of S, there was no difference among the treatments. Nevertheless, all treatments were superior to the control treatment for N and S in the shoots of wheat plants.

3.4. Antioxidant Metabolism

Selenium did not promote increases in APX, SOD, H2O2, and MDA activities (Figure 4A,C–E). On the other hand, treatments with 12, 68, and 120 g ha−1 of Se supplied via the soil promoted increases in CAT enzyme activity (Figure 4B).

3.5. Contents of Major Carbohydrates

The treatments with Se supplied via the soil positively influenced carbohydrate accumulation. The treatment with 12 g ha−1 of Se provided the highest starch content, 21 µmol g−1 of glucose in shoots, representing a 47% increase over that in the control treatment (Figure 5A). The treatment with 38 g ha−1 of Se promoted the highest increases in reducing sugar (RS) and sucrose content, about 17% and 53% higher, respectively, when compared with those in the control (Figure 5C,D). In addition, no statistical difference was observed in the total soluble sugar (TSS) contents (Figure 5B). The dose of 12 g ha−1 of Se, which provided the highest starch production, resulted in a content of 0.28 mg of Se kg−1 in the grains (Figure 2) as well as a 47% increase in the starch content in the leaves when compared with that in the control (Figure 5A).

3.6. SPAD Reading

Se-treated plants had higher Soil-Plant Analysis Development (SPAD) index values than untreated plants (Figure 6). These readings are an indirect way of quantifying the chlorophyll content of the leaves. The treatment with 12 g ha−1 of Se promoted an increase of about 5% in readings, while the treatment with 68 g ha−1 of Se increased the SPAD index even more—by 12%—when compared with the control treatment (Figure 6).

4. Discussion

The increase in biomass obtained with Se application agrees with the results found in wheat by Tao et al. [30]. In the present study, the increases in shoot biomass (Figure 1) might be a result of the beneficial effects provided by Se, such as the increase in carbohydrate and total free amino acid contents, in addition to the higher activity of some antioxidant enzymes, the higher chlorophyll index, and the accumulation of essential nutrients. Moreover, total soluble sugar (TSS) and sucrose molecules are used as a source of energy and carbon skeleton by plants, which can improve plant growth [31]. The accumulation of N and S also promotes growth due to a higher production of amino acids and a more active antioxidant system [32].
In this study, the supply of the highest Se dose (120 g ha−1) yielded a 7.98 mg of Se kg−1 dry mass, which was nearly twice as high as the values found by Keskinen et al. [33] and Ramkissoon et al. [10], which were 4.0 and 3.1 mg of Se kg−1 dry mass, respectively. In both studies, the authors used a dose of 100 g ha−1 of Se; the first was carried out in a sandy-textured soil and the second in a clayey-textured soil, which is the same soil texture of the area used in the present study.
The Se content in grains (2.27 mg kg−1) was lower than that reported by Lyons et al. [10], which was 8.32 mg of Se kg−1, in a study conducted on a clayey soil and with an applied Se dose of 120 g ha−1. However, the result is higher than that observed by Galinha et al. [34], which was 1.06 mg kg−1, after the treatment of wheat plants with a Se dose of 100 g ha−1. A pot trial performed with three Australian soils, with the application of 10 g ha−1 of Se in wheat, resulted in grain Se concentrations ranging from 0.13 to 0.84 mg kg−1 [11]. In a study performed by Liang et al. [35], Se applied via the soil resulted in increased Se concentrations, improved grain yields, and better nutritional quality in wheat due to Se incorporation into amino acids in the form of selenomethionine (Se-Met) or selenocysteine (Se-Cys), as well as the production of non-enzymatic and enzymatic antioxidants.
Comparatively, an experiment applying 2000 g ha−1 of Se in rice resulted in 0.4 and 0.9 mg of Se kg−1 in shoots when cultivated in a clayey and a sandy soil, respectively [35]. Dzomba et al. [36] found 0.19 mg of Se kg−1 in shoots of corn when applying a Se dose of 20 g ha−1 in a Eutrophic Cambisol. Even though the level of Se applied for rice in the soil is comparatively much higher than the levels used in the present study for wheat, rice is not capable of responding to Se applications. The same can be stated for corn in terms of the plant’s capacity to respond to the Se applied. The higher efficiency of wheat for accumulating Se compared to that of rice and maize may be related to the higher efficiency in plant absorption and the translocation of this element [37], as well as due to its higher protein content. Wheat plants were demonstrated to absorb approximately 12% of the Se available in sandy soil throughout the growing period, and more than 50% of the Se was accumulated in the grains [33].
The evaluation of nutrient concentrations in plant biomass is not sufficient to assess whether nutrient absorption has increased or not since it may result in incorrect data interpretation. A high concentration and low biomass may result in less accumulation than a low concentration and high biomass [38]. Therefore, it is appropriate to use the accumulation data, which are commonly calculated by multiplying the concentrations of elements in plant tissue times the weight of dry biomass [39].
Zhu et al. [40] reported increases in N, P, and K accumulation after applications of Se doses via the soil, with concentrations in the leaves of Codonopsis lanceolata ranging from 0.5 to 2 mg of Se kg−1. Boldrin et al. [41] observed that selenate application increased the S content in the shoots of eight cultivars and in the grains of five cultivars using a dose of 13 μmol L−1 of Se in a nutrient solution containing Na2SeO4 as the source of Se.
Considering the accumulation of N, Ríos et al. [42] reported that both forms of selenium (selenate and selenite) potentiated the nitrogen metabolism, but selenite was better since it induces nitrate reductase (NR), glutathione reductase (GR), and glutamate synthase (GS) activities more strongly. The increase in activity, especially for NR, may be due to the induction of the expression of genes responsive to plant hormones, which are stimulated by Se [43]. In addition, N and S are molecular components of amino acids and are present in plant tissues in an N/S ratio of about 20. Thus, plants present mechanisms to coordinate the absorption and assimilation of S and N to maintain adequate proportions of S and other amino acids for protein synthesis [44].
Possible interactions and competition between Se and other essential elements are currently a scientific point to be investigated [45]. Interactions between Se and sulfate or phosphate are widely studied due to the possible role of phosphate transporters in selenite absorption and sulfate transporters in selenate absorption [41,46]. Selenium promotes the accumulation of S by increasing the expression of sulfate transporter genes SULTR1;1, SULTR1;3, and SULTR4;1 [41]. However, the effect of Se on P absorption is still conflicting in plants. Liu et al. [47] demonstrated that P and Se absorption in the form of selenite presents antagonistic behavior, in which the increase in the P supply significantly decreased the Se concentration in the roots, stems, and leaves of winter wheat, justifying that the presence of P and S influences Se bioavailability in various plant tissues. However, Santos et al. [48] and Zhang et al. [49] observed in Panicum maximum cv. Mombaça and wheat plants, respectively, that the way Se is present in the soil influences the synergism with P, i.e., there is an accumulation of both elements only when Se is applied as selenate. The authors concluded that P possibly affects iron oxide bound to Se and organic matter bound to Se, increasing wheat Se concentrations when fertilized with selenate. On the other hand, Praus et al. [50] did not observe changes in the Se biofortification efficiency for Brassica napus via selenate (SeO42) addition with the application of P and S in the soil, while Ramos et al. [51] observed that treatments with selenite reduced P accumulation in lettuce, and selenate did not influence P accumulation. Therefore, more studies are needed to evaluate the influence of S and P on Se accumulation in crops.
Similarly to what was observed in the present study, Ramos et al. [52] reported significant increases in CAT activity when lettuce plants were submitted to nutrient solutions containing Se but did not observe increases in SOD activity. The enhancement of APX and CAT activities was also observed in Pteris vittata grown in Se-containing solutions [53]. In many cases, CAT and APX are the first enzymes to act under oxidative stress because they dismute hydrogen peroxide into water and oxygen.
MDA and H2O2 are considered good biomarkers to detect oxidative stress in plants and to monitor reactive oxygen species (ROS), while SOD, CAT, and APX antioxidant enzymes have shown the ability to reduce ROS by converting singlet oxygen into H2O2 by SOD, and then transforming H2O2 into H2O catalyzed by CAT and APX activities [54]. The greater activity of these enzymes enables plants to increase their stress tolerance, thus providing greater biomass accumulation [13]. However, the levels of hydrogen peroxide in the treatments with Se application remained similar to those in the control treatment. As previously described, APX and CAT act by dismuting H2O2, and thus, the increase in H2O2 concentration induces APX and CAT activity [53]. However, in this study, an increase was observed in CAT activity without increases in the contents of H2O2. The higher activity of the enzymes was not in response to the increase in H2O2, but rather due to the presence of Se. Kaur et al. [55] suggest that Se compounds can control the production and quenching of ROS either directly or indirectly through the regulation of the antioxidant level or/and activity.
Malondialdehyde (MDA) is a common product of lipid peroxidation, and it is used to identify injuries caused by oxidative stress [56]. Decreased lipid peroxidation by Se has a positive effect on plant antioxidant metabolism [57]. Although Se apparently did not decrease the MDA content in wheat in the present study, Iqbal et al. [58], after leaf fertilization with Se, reported a significant reduction in MDA levels. However, the decrease in MDA levels in wheat plants depends on the time of application of Se since the best results are observed when applications occur at more advanced stages of plant development, when the oxidative stress is higher due to the lower efficiency of the photosystem II, as this can generate oxygen superoxide at high concentrations [59]. In this study, sampling was performed at an early stage of vegetative growth.
Regarding the contents of major carbohydrates, Owusu-Sekyere et al. [60] observed an increase of 46% in TSS in the leaves of alfalfa plants (Medicago sativa L.) grown in the presence of Se. This value was similar to the 50% found in the treatment with 38 g ha−1 of Se in the present study. Sucu and Yagci [61] also reported increases in the TSS and starch levels in Se-treated Grape Cultivars.
In terms of starch production, Xia et al. [62] observed similar results, where the treatment that provided 0.006 g ha−1 mg of Se kg−1 in wheat kernels also provided the highest starch contents. In alfalfa, Owusu-Sekyere et al. [60] found a smaller increase in starch content (up to 36%) in leaves with Se application (15 μmol L−1) when compared with that in the present study.
Indeed, the higher carbohydrate concentration provides more substrates and structural elements for growth, culminating in higher biomass accumulation in the shoots. In addition, the accumulation of smaller chain carbohydrates may decrease water loss through respiration, as these molecules can function as osmotic and signaling agents [63]. Malik et al. [14] also attributed the higher shoot growth to the higher carbohydrate content in Se-treated beans. Increases in carbohydrate contents might occur due to a higher net photosynthetic rate [15] and the regulation of carbohydrate metabolism enzyme activities with α, β, and total amylase; invertase; and sucrose synthase [64].
The addition of Se in wheat plants via the soil stimulated the increase in total chlorophyll content in the present study. Malik et al. [13] observed that the increase in the chlorophyll content was directly proportional to the Se concentrations. The increase in total chlorophyll content was also observed by Iqbal et al. [58] in wheat and by Bocchini et al. [65] in corn after fertilization with Se. In the present study, the increase in the total chlorophyll content can be explained by the increase in N accumulation since N plays a central role in chlorophyll synthesis, so that the chlorophyll content can be used to evaluate the N status in plant leaves [66]. A higher total chlorophyll content can promote a higher electron transport flow, which is very important for winter wheat since at low temperatures the electron transport flow is negatively affected. Decreased electron transport flow may lead to a decrease in the net photosynthetic rate, due to limitations in ATP production and reducing power. In addition, an increase in the chlorophyll content can mean an increase in the photosynthetic rate, which allows for greater carbon availability for growth and grain production [67]. On the other hand, according to Lyu et al. [13], a high concentration of Se in plant cells can induce the production of reactive oxygen species, which can decrease the chlorophyll content. Thus, since in the present study there was no degradation of chlorophyll, but its increase, the applied Se concentrations were not toxic to wheat. In fact, on the contrary, Se stimulated the growth and development of wheat plants, which accumulated this element in its grains, delivering food of better nutritional quality for animals and humans.

5. Conclusions

Our findings revealed that the agronomic biofortification of wheat with selenium (as selenate) via the soil under tropical field conditions produced Se-enriched wheat grains, proving the efficiency of the method, which confirms its effectiveness as a suitable strategy for biofortification. In addition, the treatment of wheat plants with Se provided beneficial effects for the plants’ antioxidant apparatus as well as on the contents of major carbohydrates since there were increases in starch, reducing sugars, and sucrose levels. Lastly, there was an increase in the accumulation of N and S, as well as in the SPAD index. Although the increments of Se promoted biochemical and physiological benefits when compared with that of the control, it is not possible to indicate which treatment was the best since the effect on different plant systems—i.e., carbohydrates, antioxidant system, or nutrient accumulation—varied according to the concentration of Se.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/agronomy14030462/s1, Table S1: Effect of different doses of selenium applied via soil on grain yield, Se uptake, and Se absorption efficiency by wheat grains. Figure S1: Concentration of N, total aminoacids and proteins in wheat grain treated with increasing Se doses in soil.

Author Contributions

T.S.L. collected the test data and drafted the manuscript; K.R.D.d.S. helped collect data in the laboratory; F.A.D.M. helped collect data in the field; and C.d.O., A.P.B.C., E.C.d.S.J., J.H.d.L.L. and T.S.C. identified and interpreted the literature sources and helped draft the manuscript. Critical input and corrections were made by G.L. and L.R.G.G. L.R.G.G. supervised the project. All authors have read and agreed to the published version of the manuscript.

Funding

Institutions CNPq, CAPES, and FAPEMIG for providing financial support for the field experiment and the laboratory analyses. Partial funds were also provided by CNPq grant #406577/2022-6 (National Institute of Science and Technology on Soil and Food Security). The APC was funded by Program forfinancial support Qualified Scientific Production (PAPCIQ) the from Dean of Research, postgraduate studies and technological innovation (Proppit-UFOPA).

Data Availability Statement

Data are contained within the article and Supplementary Materials.

Conflicts of Interest

Author Fábio Aurélio Dias Martins was employed by the company State of Minas Gerais Agricultural Research Corporation, Epamig, Lavras. The remaining authors declare that the research was conducted in the absence of any commercial or financial rela-tionships that could be construed as a potential conflict of interest.

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Figure 1. Effect of soil Se application on plant shoot biomass of wheat. Different letters above the columns indicate significant differences among treatments at a 5% probability level (p < 0.05, n = 4) by the Scott-Knott test.
Figure 1. Effect of soil Se application on plant shoot biomass of wheat. Different letters above the columns indicate significant differences among treatments at a 5% probability level (p < 0.05, n = 4) by the Scott-Knott test.
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Figure 2. Effect of Se application via soil on Se contents (dry weight) in grains (A) and shoots (B) of wheat plants. Error bar represents standard error of mean (n = 4).
Figure 2. Effect of Se application via soil on Se contents (dry weight) in grains (A) and shoots (B) of wheat plants. Error bar represents standard error of mean (n = 4).
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Figure 3. Effect of Se application via soil on (A) nitrogen, (B) phosphorus and (C) sulfur per plot of wheat plants. Error bar represents standard error of mean (n = 4). Different letters above the columns indicate significant differences among treatments at a 5% probability level (p < 0.05, n = 4) by the Scott-Knott test.
Figure 3. Effect of Se application via soil on (A) nitrogen, (B) phosphorus and (C) sulfur per plot of wheat plants. Error bar represents standard error of mean (n = 4). Different letters above the columns indicate significant differences among treatments at a 5% probability level (p < 0.05, n = 4) by the Scott-Knott test.
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Figure 4. Effect of soil application with increasing Se doses on the enzymatic activities of ascorbate peroxidase (APX) (A), catalase (CAT) (B), superoxide ion dismutase (SOD) (C), and on the contents of hydrogen peroxide (H2O2) (D) and lipid peroxidation (MDA) (E) in wheat leaves. Different letters above the columns indicate significant differences among treatments at a 5% probability level (p < 0.05, n = 8) by the Scott-Knott test.
Figure 4. Effect of soil application with increasing Se doses on the enzymatic activities of ascorbate peroxidase (APX) (A), catalase (CAT) (B), superoxide ion dismutase (SOD) (C), and on the contents of hydrogen peroxide (H2O2) (D) and lipid peroxidation (MDA) (E) in wheat leaves. Different letters above the columns indicate significant differences among treatments at a 5% probability level (p < 0.05, n = 8) by the Scott-Knott test.
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Figure 5. Effect of soil application with increasing Se doses on reducing sugar (A), starch (B), sucrose (C), and total soluble sugar (D) levels in the shoots of wheat plants. Different letters above the columns indicate significant differences among treatments at a 5% probability level (p < 0.05, n = 8) by the Scott-Knott test.
Figure 5. Effect of soil application with increasing Se doses on reducing sugar (A), starch (B), sucrose (C), and total soluble sugar (D) levels in the shoots of wheat plants. Different letters above the columns indicate significant differences among treatments at a 5% probability level (p < 0.05, n = 8) by the Scott-Knott test.
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Figure 6. Effect of soil application with increasing Se doses on SPAD readings. Different letters above the columns indicate significant differences among treatments at a 5% probability level (p < 0.05, n = 5) by the Scott-Knott test.
Figure 6. Effect of soil application with increasing Se doses on SPAD readings. Different letters above the columns indicate significant differences among treatments at a 5% probability level (p < 0.05, n = 5) by the Scott-Knott test.
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Table 1. Physicochemical attributes of the soil used for wheat cultivation.
Table 1. Physicochemical attributes of the soil used for wheat cultivation.
pHKPCaMgAlH+AlSBTV
mg dm−3 cmolc dm−3 %
5.162.017.51.30.30.87.81.79.618.2
SOMSFeMnCuBZnClaySiltSand
g kg−1mg dm−3 g kg−1
3822.428.28.41.20.102.3420190390
SB = sum of bases: Ca2+ + Mg2+ + K; CEC = cation exchange capacity at pH 7.0; V = percentage of bases retained at a CEC; SOM = soil organic matter.
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MDPI and ACS Style

Lara, T.S.; Correia, T.S.; de Oliveira, C.; Lessa, J.H.d.L.; de Souza, K.R.D.; Corguinha, A.P.B.; da Silva, E.C., Jr.; Martins, F.A.D.; Lopes, G.; Guilherme, L.R.G. Selenium Application Provides Nutritional and Metabolic Benefits to Wheat Plants. Agronomy 2024, 14, 462. https://doi.org/10.3390/agronomy14030462

AMA Style

Lara TS, Correia TS, de Oliveira C, Lessa JHdL, de Souza KRD, Corguinha APB, da Silva EC Jr., Martins FAD, Lopes G, Guilherme LRG. Selenium Application Provides Nutritional and Metabolic Benefits to Wheat Plants. Agronomy. 2024; 14(3):462. https://doi.org/10.3390/agronomy14030462

Chicago/Turabian Style

Lara, Túlio Silva, Tatiane Santos Correia, Cynthia de Oliveira, Josimar Henrique de Lima Lessa, Kamila Rezende Dázio de Souza, Ana Paula Branco Corguinha, Ediu Carlos da Silva, Jr., Fábio Aurélio Dias Martins, Guilherme Lopes, and Luiz Roberto Guimarães Guilherme. 2024. "Selenium Application Provides Nutritional and Metabolic Benefits to Wheat Plants" Agronomy 14, no. 3: 462. https://doi.org/10.3390/agronomy14030462

APA Style

Lara, T. S., Correia, T. S., de Oliveira, C., Lessa, J. H. d. L., de Souza, K. R. D., Corguinha, A. P. B., da Silva, E. C., Jr., Martins, F. A. D., Lopes, G., & Guilherme, L. R. G. (2024). Selenium Application Provides Nutritional and Metabolic Benefits to Wheat Plants. Agronomy, 14(3), 462. https://doi.org/10.3390/agronomy14030462

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