Strategies for increasing the selenium content of wheat

Epigallocatechin gallate (EGCG) nanoselenium application improves tea quality (Camellia sinensis L.) and soil quality index without losing microbial diversity: A pot experiment under field condition

Applying selenium (Se) fertilizer is the only way to alleviate soil Se deficiency. Although effects of nanoselenium foliar application on plant growth and stress resistance have been extensively investigated, soil application of nanoselenium on soil microorganisms and their relationship with crop quality and soil health remains unclear. In this study, a steady-state homogeneous nanoparticle of epigallocatechin gallate Se (ESe) was synthesized, and a pot experiment was conducted applying ESe at five concentrations (0, 1, 10, 50, and 100 mg kg-1) to the tea planattion soil. The study revealed a significant increase in Se concentration in soil and tea with ESe application and identified 2.43-7.8 mg kg-1 as the safe and optimal range for soil application. Specifically, the moderate dose of ESe improved the tea quality [reduced tea polyphenols (TP), increased free amino acids (AA), and reduced TP/AA] and soil quality index (SQI). Besides, in marure tea leaves, antioxidant enzyme activities [promote catalase (CAT) superoxide dismutase (SOD), and peroxidase (POD)] increased, while level of oxidative stress [malondialdehyde (MDA), hydrogen peroxide (H2O2) and superoxide anion (O2-)] decreased with ESe application. The 16S rRNA of the soil bacteria showed that ESe application significantly changed the community structure of soil bacteria but did not alter the diversity of the bacteria and the abundance of dominant taxa (phylum and genus levels). Statistical analysis of the taxonomic and functional profiles (STAMP) detected 21 differential taxa (genus level), mainly low-abundance ones, under the ESe application. Linear regression and random forest (RF) modeling revealed that the low-abundance bacterial taxa were significantly correlated with SQI (R2 = 0.28, p < 0.01) and tea quality (R2 = 0.23-0.37, p < 0.01). Thus, the study's findings suggest that ESe application affects soil and tea quality by modulating the low-abundance taxa in soil. The study also highlights the crucial role of low-abundance bacterial taxa of the rhizosphere in regulating soil functions under the ESe application.

Agronomic and Genetic Strategies to Enhance Selenium Accumulation in Crops and Their Influence on Quality

Selenium (Se) is an essential trace element that plays a crucial role in maintaining the health of humans, animals, and certain plants. It is extensively present throughout the Earth's crust and is absorbed by crops in the form of selenates and selenite, eventually entering the food chain. Se biofortification is an agricultural process that employs agronomic and genetic strategies. Its goal is to enhance the mechanisms of crop uptake and the accumulation of exogenous Se, resulting in the production of crops enriched with Se. This process ultimately contributes to promoting human health. Agronomic strategies in Se biofortification aim to enhance the availability of exogenous Se in crops. Concurrently, genetic strategies focus on improving a crop's capacity to uptake, transport, and accumulate Se. Early research primarily concentrated on optimizing Se biofortification methods, improving Se fertilizer efficiency, and enhancing Se content in crops. In recent years, there has been a growing realization that Se can effectively enhance crop growth and increase crop yield, thereby contributing to alleviating food shortages. Additionally, Se has been found to promote the accumulation of macro-nutrients, antioxidants, and beneficial mineral elements in crops. The supplementation of Se biofortified foods is gradually emerging as an effective approach for promoting human dietary health and alleviating hidden hunger. Therefore, in this paper, we provide a comprehensive summary of the Se biofortification conducted over the past decade, mainly focusing on Se accumulation in crops and its impact on crop quality. We discuss various Se biofortification strategies, with an emphasis on the impact of Se fertilizer strategies on crop Se accumulation and their underlying mechanisms. Furthermore, we highlight Se's role in enhancing crop quality and offer perspective on Se biofortification in crop improvement, guiding future mechanistic explorations and applications of Se biofortification.

Selenium Biofortification Enhanced Grain Yield and Alleviated the Risk of Arsenic and Cadmium Toxicity in Rice for Human Consumption

Arsenic (As) and Cadmium (Cd) are toxic to rice plants. However, selenium (Se) has the potential to regulate As and Cd toxicity. The present study aimed to evaluate the co-exposure to As⁵⁺ and Se⁶⁺ species in two rice cultivars, BRS Pampa and EPAGRI 108. The plants were divided into six groups and cultivated until complete maturation of the grains, under greenhouse conditions. Regarding total As and inorganic As (i-As) accumulation in grains, the highest concentrations were found for BRS Pampa. For Se, EPAGRI 108 presented the highest concentration of inorganic and organic Se (i-Se and o-Se). The exposure assessments showed that Se biofortification can mitigate the As accumulation in rice and, consequently, the risk of As and Cd toxicity in grains for human consumption. The combined effect of As and Se in rice plants could represent an alternative to biofortify this food in a safe way and with a higher percentage of bioavailable Se. Although Se is able to mitigate As toxicity in rice plants, in the present study we showed that co-exposure in different cultivars under the same growing conditions may present different responses to As and Se exposure.

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

Wheat can be biofortified with different inorganic selenium (Se) forms, selenite or selenate. The choice of Se source influences the physiological response of the plant and the Se metabolites produced. We looked at selenium uptake, distribution and metabolization in wheat exposed to selenite, selenate and a 1:1 molar mixture of both to determine the impact of each treatment on the Se speciation in roots, shoots, and grains. To achieve a comprehensive quantification of the Se species, the complementarity of high-performance liquid chromatography coupled with inductively coupled plasma mass spectrometry and X-ray absorption spectroscopy was exploited. This approach allowed the identification of the six main selenium species: selenomethionine, selenocysteine, selenocystine, selenite, selenate, and elemental selenium. The three treatments resulted in similar total selenium concentration in grains, 90-150 mg Se kg^-1 , but produced different effects in the plant. Selenite enhanced root accumulation (66% of selenium) and induced the maximum toxicity, whereas selenate favored shoot translocation (46%). With the 1:1 mixture, selenium was distributed along the plant generating lower toxicity. Although all conditions resulted in >92% of organic selenium in the grain, selenate produced mainly C-Se-C forms, such as selenomethionine, while selenite (alone or in the mixture) enhanced the production of C-Se-Se-C forms, such as selenocystine, modifying the selenoamino acid composition. These results provide a better understanding of the metabolization of selenium species which is key to minimize plant toxicity and any concomitant effect that may arise due to Se-biofortification.

The importance and status of the micronutrient selenium in South Africa: a review

Selenium (Se) is a vital micronutrient with widespread biological action but leads to toxicity when taken in excessive amounts. The biological benefits of Se are mainly derived from its presence in active sites of selenoproteins such as glutathione peroxidase (GPx). An enzyme whose role is to protect tissues against oxidative stress by catalysing the reduction of peroxidase responsible for various forms of cellular damage. The benefits of Se can be harvested when proper regulations of its intake are used. In South Africa, Se distribution in people's diets and animals are low with socio-economic factors and heterogeneous spread of Se in soil throughout the country playing a significant role. The possible causes of low Se in soils may be influenced by underlying geological material, climatic conditions, and anthropogenic activities. Sedimentary rock formations show higher Se concentrations compared to igneous and metamorphic rock formations. Higher Se concentrations in soils dominates in humid and sub-humid areas of South Africa. Furthermore, atmospheric acid deposition dramatically influences the availability of Se to plants. The studies reviewed in this article have shown that atomic absorption spectroscopy (AAS) is the most utilised analytical technique for total Se concentration determination in environmental samples and there is a lack of speciation data for Se concentrations. Shortcomings in Se studies have been identified, and the future research directions of Se in South Africa have been discussed.

Effects of arbuscular mycorrhizal fungi on accumulation and translocation of selenium in winter wheat

BACKGROUND

Selenium (Se) is an essential micronutrient for humans and animals, but not for plants. Generally, cereals including wheat and rice are the main source of dietary Se for humans. Although arbuscular mycorrhizal fungi (AMF) are ubiquitous soil microbes and commonly develop symbionts with winter wheat (Triticum aestivum L.), the influence of AMF on accumulation and translocation of Se during developmental cycle of winter wheat is still unclear.

RESULTS

Based on a pot trial, the present results indicated that the effects of AMF on grain Se concentration in winter wheat depend on the Se species spiked in the soil and that Rhizophagus intraradices (Ri) significantly enhanced grain Se concentration under selenite treatment. Moreover, inoculation of AMF significantly increased grain Se content under selenite and selenate treatments. The enhanced grain Se content of mycorrhizal wheat could be attributed to (i) apparently increased root growth of mycorrhizal wheat at jointing could absorb more Se for translocating to aerial tissues and consequently result in significantly higher stalk Se content and (ii) enhancing Se translocation from vegetative tissues to grains. The present study showed that AMF significantly (P < 0.05) increased pre-anthesis Se uptake under selenate treatment and post-anthesis Se uptake under selenite treatment.

CONCLUSION

The present study indicated the feasibility of inoculation of AMF for increasing grain Se concentration under selenite treatment and enhancing the efficiency of biofortification of Se under selenate treatments. © 2022 Society of Chemical Industry.

Gibberellic acid promotes selenium accumulation in Cyphomandra betacea under selenium stress

The selenium (Se) deficiency is threatening the human health, and the increase of Se content in food can prevent the Se deficiency of human body. To increase the Se content in fruit trees and alleviate the Se stress to fruit trees, the effects of gibberellic acid (GA) on the growth and Se accumulation in Cyphomandra betacea under Se stress were studied. Although GA increased the biomass of C. betacea, it did not significantly affect the root/shoot ratio. The root and shoot biomass had a quadratic polynomial regression relationship with the GA concentration. Furthermore, GA increased the photosynthetic pigment content, photosynthetic parameters, and antioxidant enzyme activity of C. betacea. GA also increased the Se content in C. betacea, peaking at 300 mg/L GA. For instance, GA (300 mg/L) increased the Se contents in roots and shoots of C. betacea by 70.31 and 22.02%, respectively, compared with the control. Moreover, the root Se and shoot Se contents had a quadratic polynomial regression relationship with the GA concentration. Correlation and gray relational analyses showed that the carotenoid, chlorophyll a, and chlorophyll b contents were closely related to the Se uptake in C. betacea under the GA application. These results show that GA (300 mg/L) can promote the growth and Se uptake of C. betacea under Se stress.

Wet deposition of atmospheric selenium and sensitivity to emission and precipitation patterns

Wet deposition has been well recognized to be affected by species concentration and precipitation; nevertheless, the regimes in the controlling factor of concentration or precipitation have not yet been clarified. Using a trace element, selenium (Se), with dual effects on human health as a testbed, we first reproduce the spatial distribution of atmospheric Se concentrations and wet deposition fluxes through GEOS-Chem on a global scale, and examine the spatial patterns and relative importance of anthropogenic emissions vs. natural emissions over various regions around the world. We find that over most Northern Hemisphere continental regions, anthropogenic emissions are the dominant source for atmospheric Se concentration and deposition, while it is dominated by natural sources in the other areas. Nested grid simulations covering China and the continental United States are further conducted. The factors (i.e., Se concentration and precipitation) controlling the wet deposition flux of atmospheric Se are analyzed in detail, through the construction of wet deposition-concentration-precipitation (WETD-C-P) diagram for two regions (mainland China and the continental United States) based on the monthly results. The two regions show distinctive features, reflecting the different spatial patterns of Se emissions and precipitation. Both Se emissions and precipitation are higher in the eastern United States than that in the western United States. In contrast, the emissions and precipitation in northern and southern China show dipole features with stronger emissions over the northern side and higher precipitation on the southern side. We further investigate the impacts of future emission changes in China on atmospheric Se deposition and its sensitivity to emissions and precipitation, revealing a modulation of regime shifts, i.e., from the precipitation dominant regime to the concurrent governance of both precipitation and emissions. The proposed WETD-C-P relationship is useful in elucidating the regime and factors governing the spatial and temporal variations in wet deposition.

Screening of Durum Wheat Cultivars for Selenium Response under Contrasting Environments, Based on Grain Yield and Quality Attributes

In the literature, little information is available on the effect of Selenium (Se) on durum wheat yield and grain quality performances. A field investigation was conducted to explore the effect of exogenous Se foliar supply on two types of durum wheat germplasm; i.e., 16 advanced lines and nine modern varieties. The Se effect was assessed on grain yield as well as on technological quality traits (moisture, protein and gluten contents, Zeleny sedimentation index, and deformation energy) in two contrasting environments in Tunisia, namely Kef–Boulifa (semi-arid region) and Beja (sub-humid region). The results displayed significant effects of environments, Se foliar application, and cultivars on grain yield and quality attributes. For grain yield performance, the beneficial effect of Se was more pronounced under the Kef–Boulifa environment, and conversely for the grain quality. A genetic variation was observed within and among the two environments under both Se treatments (with and without Se). Notably, the Se-treated advanced lines displayed the highest grain yield under Kef–Boulifa and Beja conditions. Although these cultivars showed better grain quality in both sites, the modern varieties valorized the Se foliar application better. Cultivars that recorded the highest values for the studies attributes were not necessarily those that valorized the Se supply better. Interestingly, some advanced lines have noted superiority compared to the modern varieties. In this study, cultivars that combine both good yield and good grain quality were determined for semi-arid (L11, L1, Dhahbi, and Maali) and sub-humid (L2, L14, L6, L3, Salim, and INRAT 100) zones. The screening results provide genetic material that could be exploited in breeding programs to improve Se use efficiency.

Amino acid promotes selenium uptake in medicinal plant Plantago asiatica

The medicinal plant, Plantago asiatica have high selenium (Se) accumulation ability but is considered lower compared to other Se-hyperaccumulators. In this experiment, we evaluated the effects of different amino acid concentrations (600, 900, 1200, and 1500-fold dilutions) on the growth and Se uptake in P. asiatica for possible improvement of Se accumulation ability and medicinal value of P. asiatica. The 600, 900, and 1200-fold amino acid dilutions increased the root and shoot biomass of P. asiatica. Additionally, the photosynthetic pigments contents (chlorophyll a, chlorophyll b, and total chlorophyll) and antioxidant enzymes activities (superoxide dismutase, peroxidase, and catalase) of P. asiatica were increased by the different amino acid concentrations. However, these amino acid concentrations reduced the soluble protein content of P. asiatica to some extent. The Se content and extraction from P. asiatica were also enhanced and had a quadratic polynomial regression relationship with the Se extraction tissues and their Se contents. In addition, there were significant correlations between the biomass of Se extraction tissues and their Se contents. Our findings indicate that various amino acid concentrations promote growth and Se uptake in P. asiatica, but 900-fold amino acid dilution is the best concentration for enhancing Se accumulation ability in P. asiatica shoots.

Selenium in Wheat from Farming to Food

Selenium (Se) plays an important role in human health. Approximately 80% of the world's population does not consume enough Se recommended by the World Health Organization. Wheat is an important staple food and Se source for most people in the world. This review summarizes literature about Se from 1936 to 2020 to investigate Se in wheat farming soil, wheat, and its derived foods. Se fortification and the recommended Se level in wheat were also discussed. Results showed that Se contents in wheat farming soil, grain, and its derived foods around the world were 3.8-552 μg kg^-1 (mean of 220.99 μg kg^-1), 0-8270 μg kg^-1 (mean of 347.30 μg kg^-1), and 15-2372 μg kg^-1 (mean of 211.86 μg kg^-1), respectively. Adopting suitable agronomic measures could effectively realize Se fortification in wheat. The contents in grain, flour, and its derived foods could be improved from 93.94 to 1181.92 μg kg^-1, from 73.06 to 1007.75 μg kg^-1, and from 86.90 to 587.61 μg kg^-1 on average after leaf Se fertilizer application in the field. There was a significant positive correlation between the Se content in farming soil and grain, and it was extremely the same between the foliar Se fertilizer concentration rate and the grain Se increased rate. The recommended Se fortification level in cultivation of wheat in China, India, and Spain was 18.53-23.96, 2.65-3.37, and 3.93-9.88 g hm^-2, respectively. Milling processing and food type could greatly affect the Se content of wheat-derived food and should be considered seriously to meet people's Se requirement by wheat.

Selenium Biofortification Modulates Plant Growth, Microelement and Heavy Metal Concentrations, Selenium Uptake, and Accumulation in Black-Grained Wheat

In Se-deficient populations, Selenium- (Se-) enriched wheat is a source of Se supplementation, and Se content can be improved by agronomic biofortification. Thus, black-grained wheat (BGW) and white-grained wheat (WGW) (as the control) were grown in Se naturally contained soils at different concentrations (11.02, 2.21, 2.02, and 0.20 mg·kg-1). Then, a field experiment was conducted to assess agronomic performance, the concentration of microelements and heavy metals, and the uptake and distribution of Se in the BGW under the application of Se ore powder. The results showed that the grain yield and grain Se concentration of wheat respectively show a significant increase and decrease from high Se to low Se areas. Higher grain yield and crude protein content were observed in Se-rich areas. The soil application of Se ore powder increased wheat grain yield and its components (biomass, harvest index, grain number, and 1,000 kernels weight). The concentrations of Zn, Fe, Mn, total Se, and organic Se in the grains of wheat were also increased, but Cu concentration was decreased. The concentrations of Pb, As, Hg, and Cr in wheat grains were below the China food regulation limits following the soil application of Se ore powder. Compared with the control, Se ore powder treatment increased the uptake of Se in various parts of wheat plants. More Se accumulation was observed in roots following Se ore powder application, with a smaller amount in grains. In addition, compared with the control, BGW had significantly higher concentrations of Zn, Fe, and Mn and accumulated more Se in grains and shoots and less Se in roots. The results indicate that wheat grown in Se-rich areas increases its grain yield and crude protein content. The soil application of Se ore powder promotes wheat growth and grain yield. Compared with WGW, BGW accumulated more Se in grains and had a higher concentration of organic Se in grains. In conclusion, the application of Se ore powder from Ziyang as Se-enriched fertilizer could be a promising strategy for Se biofortification in the case of wheat, and BGW is the most Se-rich potential genotype.

Wheat/Gluten-Related Disorders and Gluten-Free Diet Misconceptions: A Review

In the last 10,000 years, wheat has become one of the most important cereals in the human diet and today, it is widely consumed in many processed food products. Mostly considered a source of energy, wheat also contains other essential nutrients, including fiber, proteins, and minor components, such as phytochemicals, vitamins, lipids, and minerals, that together promote a healthy diet. Apart from its nutritional properties, wheat has a set of proteins, the gluten, which confer key technical properties, but also trigger severe immune-mediated diseases, such as celiac disease. We are currently witnessing a rise in the number of people adhering to gluten-free diets unwarranted by any medical need. In this dynamic context, this review aims to critically discuss the nutritional components of wheat, highlighting both the health benefits and wheat/gluten-related disorders, in order to address common misconceptions associated with wheat consumption.

The Effect of Foliar Selenium (Se) Treatment on Growth, Photosynthesis, and Oxidative-Nitrosative Signalling of Stevia rebaudiana Leaves

Selenium (Se) enrichment of Stevia rebaudiana Bertoni can serve a dual purpose, on the one hand to increase plant biomass and stress tolerance and on the other hand to produce Se fortified plant-based food. Foliar Se spraying (0, 6, 8, 10 mg/L selenate, 14 days) of Stevia plantlets resulted in slightly decreased stevioside and rebaudioside A concentrations, and it also caused significant increment in stem elongation, leaf number, and Se content, suggesting that foliar Se supplementation can be used as a biofortifying approach. Furthermore, Se slightly limited photosynthetic CO₂ assimilation (A_N, g_sw, C_i/C_a), but exerted no significant effect on chlorophyll, carotenoid contents and on parameters associated with photosystem II (PSII) activity (F_V/F_M, F₀, Y(NO)), indicating that Se causes no photodamage in PSII. Further results indicate that Se is able to activate PSI-cyclic electron flow independent protection mechanisms of the photosynthetic apparatus of Stevia plants. The applied Se activated superoxide dismutase (SOD) isoenzymes (MnSOD1, FeSOD1, FeSOD2, Cu/ZnSOD1, Cu/ZnSOD2) and down-regulated NADPH oxidase suggesting the Se-induced limitation of superoxide anion levels and consequent oxidative signalling in Stevia leaves. Additionally, the decrease in S-nitrosoglutathione reductase protein abundance and the intensification of protein tyrosine nitration indicate Se-triggered nitrosative signalling. Collectively, these results suggest that Se supplementation alters Stevia shoot morphology without significantly affecting biomass yield and photosynthesis, but increasing Se content and performing antioxidant effects, which indicates that foliar application of Se may be a promising method in Stevia cultivation.

Biofortification and bioavailability of Zn, Fe and Se in wheat: present status and future prospects

Knowledge of genetic variation, genetics, physiology/molecular basis and breeding (including biotechnological approaches) for biofortification and bioavailability for Zn, Fe and Se will help in developing nutritionally improved wheat. Biofortification of wheat cultivars for micronutrients is a priority research area for wheat geneticists and breeders. It is known that during breeding of wheat cultivars for productivity and quality, a loss of grain micronutrient contents occurred, leading to decline in nutritional quality of wheat grain. Keeping this in view, major efforts have been made during the last two decades for achieving biofortification and bioavailability of wheat grain for micronutrients including Zn, Fe and Se. The studies conducted so far included evaluation of gene pools for contents of not only grain micronutrients as above, but also for phytic acid (PA) or phytate and phytase, so that, while breeding for the micronutrients, bioavailability is also improved. For this purpose, QTL interval mapping and GWAS were carried out to identify QTLs/genes and associated markers that were subsequently used for marker-assisted selection (MAS) during breeding for biofortification. Studies have also been conducted to understand the physiology and molecular basis of biofortification, which also allowed identification of genes for uptake, transport and storage of micronutrients. Transgenics using transgenes have also been produced. The breeding efforts led to the development of at least a dozen cultivars with improved contents of grain micronutrients, although land area occupied by these biofortified cultivars is still marginal. In this review, the available information on different aspects of biofortification and bioavailability of micronutrients including Zn, Fe and Se in wheat has been reviewed for the benefit of those, who plan to start work or already conducting research in this area.

Regulation of Selenium/Sulfur Interactions to Enhance Chemopreventive Effects: Lessons to Learn from Brassicaceae

Selenium (Se) is an essential trace element, which represents an integral part of glutathione peroxidase and other selenoproteins involved in the protection of cells against oxidative damage. Selenomethionine (SeMet), selenocysteine (SeCys), and methylselenocysteine (MeSeCys) are the forms of Se that occur in living systems. Se-containing compounds have been found to reduce carcinogenesis of animal models, and dietary supplemental Se might decrease cancer risk. Se is mainly taken up by plant roots in the form of selenate via high-affinity sulfate transporters. Consequently, owing to the chemical similarity between Se and sulfur (S), the availability of S plays a key role in Se accumulation owing to competition effects in absorption, translocation, and assimilation. Moreover, naturally occurring S-containing compounds have proven to exhibit anticancer potential, in addition to other bioactivities. Therefore, it is important to understand the interaction between Se and S, which depends on Se/S ratio in the plant or/and in the growth medium. Brassicaceae (also known as cabbage or mustard family) is an important family of flowering plants that are grown worldwide and have a vital role in agriculture and populations’ health. In this review we discuss the distribution and further interactions between S and Se in Brassicaceae and provide several examples of Se or Se/S biofortifications’ experiments in brassica vegetables that induced the chemopreventive effects of these crops by enhancing the production of Se- or/and S-containing natural compounds. Extensive further research is required to understand Se/S uptake, translocation, and assimilation and to investigate their potential role in producing anticancer drugs.

Effects of selenium on macro- and micro nutrients and selected qualitative parameters of oat (Avena sativa L.)

The article deals with the effect of foliar Se application on macro-and micro-elements and selected quantitative parameters (the content of ash, starch, and fat) in oat grains. The three-year experiments were carried out on Research and Breeding Station Vígľaš – Pstruša in the years 2014, 2015, 2016. The used oat variety was Valentin. The experiment was performed by a block method within a parcel size of 10 square meters (8 x 1.25 m) with the span of rows amounting to 0.125 m in four replications. Alfalfa was grown as forecrop. A potato and wheat production area (III-C2) with a height of 375 m above the sea level. The experimental area is characterized by warm, slightly wet weather with an average annual temperature of 7.8 °C and average annual precipitations of 666 mm. Basic fertilizing was planned before the sowing in the form of 100 kg of Ammonium nitrate containing dolomite (27% N), 100 kg of 60% KCl (60% of K2O), and100 kg of MAP (Monoammonium phosphate 12% N and 52% P2O5). Selenium was foliar applied in doses 25 g and 50 g Se per hectare in a solution form of sodium selenate (Na2SeO4). The harvest was realized by a small plot harvester in BBCH 91. The results of the experiments showed a statistically non-significant effect on microelements and most macroelements. Only sulfur content in oat grains was statistically significantly influenced by Se foliar treatment. The contents of ash, starch, and fat in oat grains were monitored, which showed statistically significant effect only in fat. Se content in grains showed a statistically significant increase by both Se foliar treatments.

Selenium Uptake by Lettuce (Lactuca sativa L.) and Berseem (Trifolium alexandrinum L.) as Affected by the Application of Sodium Selenate, Soil Acidity and Organic Matter Content

Selenium deficiency in humans and animals can be reduced through dietary supplementation. Therefore, Se biofortification strategy is important in food plants and pastures. In this study, the effects of selenium (Se) addition (4 mg Se/kg) as sodium selenate (Na₂SeO₄) on lettuce (Lactuca Sativa L.) and berseem cultivation (Trifolium alexandrinum L.) were investigated. The experiment was conducted under greenhouse conditions with two different soil types, an acidic (pH = 6.3) and an alkaline (pH = 8.0) soil with different organic matter content, in a completely randomized design. The results indicated higher Se content in berseem cultivated on acidic soil. It was also observed a significant reduction (~ 45%) in plant biomass of lettuce in the acidic soil combined with Se application. The results showed that leaf Se content was negatively correlated with soil organic matter. The decreased Se content in plants cultivated on the alkaline soil with high organic matter content support that the effect of pH on Se uptake decreased as the soil organic matter content increased.

Lactic Acid Fermentation of Cereals and Pseudocereals: Ancient Nutritional Biotechnologies with Modern Applications

Grains are a substantial source of macronutrients and energy for humans. Lactic acid (LA) fermentation is the oldest and most popular way to improve the functionality, nutritional value, taste, appearance and safety of cereal foods and reduce the energy required for cooking. This literature review discusses lactic acid fermentation of the most commonly used cereals and pseudocereals by examination of the microbiological and biochemical fundamentals of the process. The study provides a critical overview of the indispensable participation of lactic acid bacteria (LAB) in the production of many traditional, ethnic, ancient and modern fermented cereals and beverages, as the analysed literature covers 40 years. The results reveal that the functional aspects of LAB fermented foods are due to significant molecular changes in macronutrients during LA fermentation. Through the action of a vast microbial enzymatic pool, LAB form a broad spectrum of volatile compounds, bioactive peptides and oligosaccharides with prebiotic potential. Modern applications of this ancient bioprocess include the industrial production of probiotic sourdough, fortified pasta, cereal beverages and "boutique" pseudocereal bread. These goods are very promising in broadening the daily menu of consumers with special nutritional needs.

Agronomic biofortification with selenium impacts storage proteins in grains of upland rice

BACKGROUND

Selenium (Se) is an essential element for humans and animals. Rice is one of the most commonly consumed cereals in the world, so the agronomic biofortification of cereals with Se may be a good strategy to increase the levels of daily intake of Se by the population. This study evaluated the agronomic biofortification of rice genotypes with Se and its effects on grain nutritional quality. Five rates of Se (0, 10, 25, 50, and 100 g ha ^-1 ) were applied as selenate via the soil to three rice genotypes under field conditions.

RESULTS

Selenium concentrations in the leaves and polished grains increased linearly in response to Se application rates. A highly significant correlation was observed between the Se rates and the Se concentration in the leaves and grains, indicating high translocation of Se. The application of Se also increased the concentration of albumin, globulin, prolamin, and glutelin in polished grains.

CONCLUSION

Biofortifying rice genotypes using 25 g Se ha ^-1 could increase the average daily Se intake from 4.64 to 66 μg day^-1 . Considering that the recommended daily intake of Se by adults is 55 μg day^-1 , this agronomic strategy could contribute to alleviating widespread Se malnutrition. © 2019 Society of Chemical Industry.

Effect of selenium in soil on the toxicity and uptake of arsenic in rice plant

Selenium can regulate arsenic toxicity by strengthening antioxidant potential, but the antagonism between selenite or selenate nutrient and the translocation of arsenic species from paddy soil to different rice organs are poorly understood. In this study, a pot experiment was designed to investigate the effect of selenite or selenate on arsenite or arsenate toxicity to two indica rice cultivars (namely Ming Hui 63 and Lu You Ming Zhan), and the uptake and transportation of arsenic species from paddy soil to different rice organs. The results showed that selenite or selenate could significantly decrease the arsenate concentration in pore water of soils, and thus inhibited arsenate uptake by rice roots. However, the existence of selenite or selenate didn't decrease arsenate concentration in rhizosphere pore water of two indica rice cultivars. There existed good antagonistic effect between selenite or selenate and the uptake of arsenite and arsenate in rice plant in the case of low arsenic paddy soil. However, this antagonism depended on rice cultivars, arsenic species and arsenic level in soil. There existed both synergistic and inhibiting effects between the addition of selenite or selenate and the uptake of trimethylarsinoxide and dimethylarsinic acid by two indica rice cultivars, but the mechanism was unclear. Both selenite and selenate are all effective to decrease the translocation of inorganic arsenic from the roots to their above-ground rice organs in arsenite/arsenate-spiked paddy soil, but selenate had stronger inhibiting effect on their transfer factors than selenite.

Selenium Uptake and Biotransformation in Brassica rapa Supplied with Selenite and Selenate: A Hydroponic Work with HPLC Speciation and RNA-Sequencing

Vegetables are an ideal source of human Se intake; it is important to understand selenium (Se) speciation in plants due to the distinct biological functions of selenocompounds. In this hydroponic study, the accumulation and assimilation of selenite and selenate in pak choi (Brassica rapa), a vastly consumed vegetable, were investigated at 1-168 h with HPLC speciation and RNA-sequencing. The results showed that the Se content in shoots and Se translocation factors with selenate addition were at least 10.81 and 11.62 times, respectively, higher than those with selenite addition. Selenite and selenate up-regulated the expression of SULT1;1 and PHT1;2 in roots by over 240% and 400%, respectively. Selenite addition always led to higher proportions of seleno-amino acids, while SeO₄^2- was dominant under selenate addition (>49% of all Se species in shoots). However, in roots, SeO₄^2- proportions declined substantially by 51% with a significant increase of selenomethionine proportions (63%) from 1 to 168 h. Moreover, with enhanced transcript of methionine gamma-lyase (60% of up-regulation compared to the control) plus high levels of methylselenium in shoots (approximately 70% of all Se species), almost 40% of Se was lost during the exposure under the selenite treatment. This work provides evidence that pak choi can rapidly transform selenite to methylselenium, and it is promising to use the plant for Se biofortification.

Mortality, growth and metabolic responses by 1H-NMR-based metabolomics of earthworms to sodium selenite exposure in soils

The rapid development of selenium-enriched agriculture leads to the accumulation of selenium in the soil, which has an adverse impact on terrestrial ecosystems. In the present study, the mortality, growth inhibition rate and metabolism of earthworms were examined to investigate the toxicological effects of sodium selenite (Na₂SeO₃) on earthworms (Eisenia fetida) after exposuring for 14 days (d). We used ¹H-NMR-based metabolomics to identify sensitive biomarkers and explored the metabolic responses of earthworms exposed to Na₂SeO₃. The mortality and growth inhibition rate of earthworms exposed to 70 and 90 mg/kg Na₂SeO₃ were significantly higher than the rate of control group. The LC₅₀ (the median lethal concentration) of Na₂SeO₃ was 57.4 mg/kg in this artificial soil test of E. fetida exposed to Na₂SeO₃ for 14 d. However, there was no significant differences when earthworms were exposed to different concentrations of Na₂SeO₃. The selected metabolic markers were ATP, lactic acid, leucine, alanine, valine, glycine, glutamic acid, lysine, α-glucose and betaine. Na₂SeO₃ affected the metabolic level of earthworms, as the percentage of metabolic markers in the earthworm changes when exposed to different concentrations of Na₂SeO₃. The metabolic disturbances were greater with increasing concentrations of Na₂SeO₃. The differential metabolic markers were significantly changed when exposed to Na₂SeO₃ comparing to those in the control group, affecting the tricarboxylic acid cycle process and breaking the metabolic balance. This study showed that Na₂SeO₃ had toxic effect on the growth and development of earthworms. In addition, this study provided a biochemical insights for the development of selenium-enriched agriculture.

NRT1.1B improves selenium concentrations in rice grains by facilitating selenomethinone translocation

Selenium (Se) is an essential trace element for humans and other animals, yet approximately one billion people worldwide suffer from Se deficiency. Rice is a staple food for over half of the world's population that is a major dietary source of Se. In paddy soils, rice roots mainly take up selenite. Se speciation analysis indicated that most of the selenite absorbed by rice is predominantly transformed into selenomethinone (SeMet) and retained in roots. However, the mechanism by which SeMet is transported in plants remains largely unknown. In this study, SeMet uptake was found to be an energy-dependent symport process involving H⁺ transport, with neutral amino acids strongly inhibiting SeMet uptake. We further revealed that NRT1.1B, a member of rice peptide transporter (PTR) family which plays an important role in nitrate uptake and transport in rice, displays SeMet transport activity in yeast and Xenopus oocyte. The uptake rate of SeMet in the roots and its accumulation rate in the shoots of nrt1.1b mutant were significantly repressed. Conversely, the overexpression of NRT1.1B in rice significantly promoted SeMet translocation from roots to shoots, resulting in increased Se concentrations in shoots and rice grains. With vascular-specific expression of NRT1.1B, the grain Se concentration was 1.83-fold higher than that of wild type. These results strongly demonstrate that NRT1.1B holds great potential for the improvement of Se concentrations in grains by facilitating SeMet translocation, and the findings provide novel insight into breeding of Se-enriched rice varieties.

Combating Micronutrient Deficiency and Enhancing Food Functional Quality Through Selenium Fortification of Select Lettuce Genotypes Grown in a Closed Soilless System

Selenium (Se) is an essential trace element for human nutrition and a key component of selenoproteins having fundamental biological and nutraceutical functions. We currently examined lettuce biofortification with Se in an open-gas-exchange growth chamber using closed soilless cultivation for delivering Se-rich food. Morphometric traits, minerals, phenolic acids, and carotenoids of two differently pigmented Salanova cultivars were evaluated in response to six Se concentrations (0-40 μM) delivered as sodium selenate in the nutrient solution. All treatments reduced green lettuce fresh yield slightly (9%), while a decrease in red lettuce was observed only at 32 and 40 μM Se (11 and 21% respectively). Leaf Se content increased in both cultivars, with the red accumulating 57% more Se than the green. At 16 μM Se all detected phenolic acids increased, moreover a substantial increase in anthocyanins (184%) was recorded in red Salanova. Selenium applications slightly reduced the carotenoids content of green Salanova, whereas in red Salanova treated with 32 μM Se violaxanthin + neoxanthin, lutein and β-cryptoxanthin spiked by 38.6, 27.4, and 23.1%, respectively. Lettuce constitutes an ideal target crop for selenium biofortification and closed soilless cultivation comprises an effective tool for producing Se-enriched foods of high nutraceutical value.

Characteristics of Time-Dependent Selenium Biofortification of Rice ( Oryza sativa L.)

The application of selenite to soil has increasingly been used to produce Se-enriched food. This study investigated the biofortification characteristics of Se in rice after application of selenite to soil at different growth stages. The results showed that the application of Se during booting stage resulted in the highest concentration of Se in brown rice due to the highest upward translocation of Se. More than 90% of Se in the brown rice was organic species, with selenomethionine predominated. The proportion of selenomethionine in the brown rice decreased with the delay in application time. The rice grown in the acidic soil had higher Se concentrations than in the neutral soil. With increasing soil Cd level, Se accumulation and the proportion of Se-methylselenocysteine in the brown rice were reduced. This study provides a theoretical basis for the production of Se-enriched rice in clean soil or slightly to moderately Cd-contaminated soil.

Action of selenium against Sclerotinia sclerotiorum: Damaging membrane system and interfering with metabolism

Selenium (Se) in soil is beneficial for environmental stress tolerance of plants, and it has widespread toxic effects on pathogens. Based on the fact that Se significantly inhibited the growth of Sclerotinia sclerotiorum, we set experiments with different concentrations of Se to investigate the action of Se against S. sclerotiorum in this study. The results showed that Se (>0.5 mg L^-1) changed the morphology of S. sclerotiorum mycelia, and higher Se concentrations severely damaged mycelial structures. Fourier transform infrared spectroscopy (FTIR) analysis indicated that Se treatment induced the chemical composition of mycelia with much abundance of functional groups such as alcohols, ketones, ammonium and esters, and 0.5 mg L^-1 Se maximized their concentrations. Under Se treatments, the electrical conductivity of mycelia increased in a time-dependent manner, and osmolyte concentrations of mycelia increased as well. Se supplementation significantly reduced polymethylgalacturonase (PMG) and carboxymethylcellulase (Cx) activities, which protecting plants from infection, and increased the energy expenditure in S. sclerotiorum. Combined action of Se damage on membrane system, osmoregulation, reduction of cell wall degrading enzymes activities and improvement of energy expenditure resulted in the inhibition of S. sclerotiorum growth. Findings in this study provided evidences for using Se as a potential fungicide to control S. sclerotiorum.

Effect of selenium-enriched organic material amendment on selenium fraction transformation and bioavailability in soil

To exploit the plant byproducts from selenium (Se) biofortification and reduce environmental risk of inorganic Se fertilizer, pot experiment was conducted in this study. The effects of Se-enriched wheat (Triticum aestivum L.) straw (WS + Se) and pak choi (Brassica chinensis L.) (P + Se) amendment on organo-selenium speciation transformation in soil and its bioavailability was evaluated by pak choi uptake. The Se contents of the cultivated pak choi in treatments amended with the same amount of Se-enriched wheat straw and pak choi were 1.7 and 9.7 times in the shoots and 2.3 and 6.3 times in the roots compared with control treatment. Soil respiration rate was significantly increased after all organic material amendment in soil (p < 0.05), which accelerated the mineralization of organic materials and thus resulted in soluble Se (SOL-Se), exchangeable Se (EX-Se), and fulvic acid-bound Se (FA-Se) fraction increasing by 25.2-29.2%, 9-13.8%, and 4.92-8.28%, respectively. In addition, both Pearson correlation and cluster analysis showed that EX-Se and FA-Se were better indicators for soil Se availability in organic material amendment soils. The Marquardt-Levenberg Model well described the dynamic kinetics of FA-Se content after Se-enriched organic material amendment in soil mainly because of the mineralization of organic carbon and organo-selenium. The utilization of Se in P + Se treatment was significantly higher than those in WS + Se treatment because of the different mineralization rates and the amount of FA-Se in soil. Se-enriched organic materials amendment can not only increase the availability of selenium in soil but also avoid the waste of valuable Se source.

Do ancient types of wheat have health benefits compared with modern bread wheat?

A number of studies have suggested that ancient wheats have health benefits compared with modern bread wheat. However, the mechanisms are unclear and limited numbers of genotypes have been studied, with a particular focus on Kamut^® (Khorasan wheat). This is important because published analyses have shown wide variation in composition between genotypes, with further effects of growth conditions. The present article therefore critically reviews published comparisons of the health benefits of ancient and modern wheats, in relation to the selection and growth of the lines, including dietary interventions and comparisons of adverse effects (allergy, intolerance, sensitivity). It is concluded that further studies are urgently required, particularly from a wider range of research groups, but also on a wider range of genotypes of ancient and modern wheat species. Furthermore, although most published studies have made efforts to ensure the comparability of material in terms of growth conditions and processing, it is essential that these are standardised in future studies and this should perhaps be a condition of publication.

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Critically appraises the health benefits of ancient wheats in relationship to grain composition.

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Includes human intervention trials and in vitro studies.

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Included metabolic and adverse effects.

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Makes recommendations for future work.

Selenium Enrichment of Horticultural Crops

The ability of some crops to accumulate selenium (Se) is crucial for human nutrition and health. Selenium has been identified as a cofactor of the enzyme glutathione peroxidase, which is a catalyzer in the reduction of peroxides that can damage cells and tissues, and can act as an antioxidant. Plants are the first link in the food chain, which ends with humans. Increasing the Se quantity in plant products, including leafy and fruity vegetables, and fruit crops, without exceeding the toxic threshold, is thus a good way to increase animal and human Se intake, with positive effects on long-term health. In many Se-enriched plants, most Se is in its major organic form. Given that this form is more available to humans and more efficient in increasing the selenium content than inorganic forms, the consumption of Se-enriched plants appears to be beneficial. An antioxidant effect of Se has been detected in Se-enriched vegetables and fruit crops due to an improved antioxidative status and to a reduced biosynthesis of ethylene, which is the hormone with a primary role in plant senescence and fruit ripening. This thus highlights the possible positive effect of Se in preserving a longer shelf-life and longer-lasting quality.

Concentrations of minerals in pig feed ingredients commonly used in China

Mineral concentrations were determined in 13 different feed ingredients commonly used in swine diets. Ingredients included corn and 4 corn co-products: corn gluten feed, corn gluten meal, corn germ meal, and corn distillers dried grains with solubles (DDGS). Wheat, wheat bran, and wheat shorts were also included, and 5 oilseed meals including soybean meal, rapeseed meal, sunflower meal, cottonseed meal, and peanut meal were used as well. Corn grain contained 88.7% dry matter (DM) and 0.46% K (DM basis). Greater concentrations of DM, ash, Ca, P, nonphytate P, Cu, Fe, Mn, and Zn were observed in corn gluten feed, corn DDGS, and corn germ meal compared with corn grain (P < 0.05). In general, minerals in corn DDGS were approximately three times greater than in corn grain and about 90% of the total P in corn DDGS was in the nonphytate bound form. Corn gluten meal had the least concentrations (P < 0.05) of most minerals, but the greatest (P < 0.05) concentrations of Fe (373.55 mg/kg, DM basis), Cu (11.88 mg/kg, DM basis), and Se (0.92 mg/kg, DM basis). On a DM-basis, concentrations of DM, Ca, P, phytate bound P, and Fe in wheat grain were 88.2%, 0.10%, 0.34%, 0.16%, and 53.48 mg/kg, respectively. Wheat bran contained more (P < 0.05) K, Mg, Cl, Fe, Zn, and Mn compared with wheat and wheat shorts. On a DM-basis, 2.72% K was observed in soybean meal, which was more (P < 0.05) than in the other oilseed meals. However, rapeseed meal had the greatest (P < 0.05) concentration of ash (9.37%), Ca (1.01%), P (1.05%), and Fe (526.49 mg/kg) among the oilseed meals, but only 16.2% of the total P in rapeseed meal was non-phytate P. In contrast, more than 50% of the P in soybean meal and peanut meal was non-phytate P. The least (P < 0.05) concentration of Cu (6.73 mg/kg, DM basis) was observed in rapeseed meal and the greatest (P < 0.05) concentration (32.75 mg/kg) was analyzed in sunflower meal. Concentrations of most minerals in soybean meal, rapeseed meal, sunflower meal, cottonseed meal, and peanut meal varied considerably compared with published values. In conclusion, the concentration of minerals in 13 commonly used feed ingredients were analyzed and results indicated considerable variation among and within feed ingredients for most minerals, which for some minerals may be a result of differences in minerals in the soil in which the ingredients were grown, but processing likely also contributes to differences among ingredients.

Effects of selenite and selenate application on distribution and transformation of selenium fractions in soil and its bioavailability for wheat (Triticum aestivum L.)

This study investigated the effect of selenate and selenite application on the distribution, transformation of selenium (Se) fractions in soil, as well as the accumulation and availability of Se in each part of wheat plants. A pot experiment was conducted using different concentrations of exogenous selenite or selenate (0.5, 1, 2.5, 5, and 10 mg Se kg^-1 soil). Sequential extraction was used to determine the Se fractions in soil, and different models were used to study the behavior of Se in soil and its availability to wheat. Results showed that the distribution and availability of Se in soil and its accumulation in wheat affected both by Se concentrations and forms of exogenous Se. In selenite-treated soil, the proportion of exchangeable and carbonate-bound Se (EXC-Se) (21-42%) fraction increased compared to that in control (12%), while organic matter-bound Se (OM-Se) (23-33%) and Fe-Mn oxide-bound Se (FMO-Se) (11-15%) fractions decreased compare with those in control (37 and 32%, respectively). In selenate-treated soil, soluble-Se (SOL-Se) fraction (30-54%) increased and the OM-Se (9.8-20%) and FMO-Se (4.7-14.2%) fractions decreased compared with those in control. Residual Se (RES-Se) fraction was increased for selenite (7.4-13.4%) and selenate (12-20%) treatments compared with that in control (6.5%). In comparison with control, the available Se (SOL-Se + EXC-Se) fraction increased for both selenite (32-47%) or selenate (54-72%) treatments. Moreover, at the same rate of Se application, Se availability was higher in wheat grown in selenate-treated soils than that in selenite-treated soils. The redistribution index (U _ts) of Se increased from 1 (in control) to 1.2-1.9 and 1.5-2 for selenite and selenate treatments, respectively; additionally, the mobility factor (MF) in selenate-treated soil was 40-90% higher than that in selenite-treated soil. Furthermore, relative bonding intensity (I _R ) for both selenite (0.38-0.45) and selenate treatment (0.33-0.41) decreased compared with that in control (0.55). These differences indicated that selenite and selenate varied in terms of fixation capacities in soil, in transformation and distribution of Se in soil fractions, and in their availability to plants. The results of Michaelis-Menten equation demonstrated the high affinity of leaf to selenate, and the high affinity of roots and grains to selenite. Selenate was dominant in nearly all parts of wheat plants and in each application level. However, the affinity of selenite to wheat grains suggests that selenite is a useful Se fertilizer that must be considered in biofortification programs. In-depth studies at the pot and field scales by using different wheat varieties and application methods of Se in different ecological zones must be conducted to elucidate the mechanism and biochemical properties of Se in soil-plant system and ultimately produce Se-rich staple foods.

Effects of Different Forms of Selenium Fertilizers on Se Accumulation, Distribution, and Residual Effect in Winter Wheat-Summer Maize Rotation System

Foliar Se fertilizers were applied to investigate the effects of Se forms on Se accumulation and distribution in the wheat-maize rotation system and residual concentration of Se in subsequent crops. Sodium selenite, sodium selenate, selenomethionine, chemical nano-Se, humic acid + sodium selenite, and compound fertilizer + sodium selenite were applied once at the flowering stage of wheat (30 g ha^-1) and at the bell stage of maize (60 g ha^-1). Compared with the control treatment, foliar Se applications significant increased the grain Se concentration of wheat and maize by 0.02-0.31 and 0.07-1.09 mg kg^-1, respectively. Wheat and maize grain Se recoveries were 3.0-10.4 and 4.1-18.5%, respectively. However, Se concentrations in the grain of subsequent wheat and maize significantly decreased by 77.9 and 91.2%, respectively. The change of Se concentration in soil was a dynamic process with Se depletion after harvest of maize.

Influence of Se concentrations and species in hydroponic cultures on Se uptake, translocation and assimilation in non-accumulator ryegrass

The success of biofortification and phytoremediation practices, addressing Se deficiency and Se pollution issues, hinges crucially on the fate of selenium in the plant media in response to uptake, translocation and assimilation processes. We investigate the fate of selenium in root and shoot compartments after 3 and 6 weeks of experiment using a total of 128 plants grown in hydroponic solution supplied with 0.2, 2, 5, 20 and 100 mg L^-1 of selenium in the form of selenite, selenate and a mixture of both species. Selenate-treated plants exhibited higher root-to-shoot Se translocation and total Se uptake than selenite-treated plants. Plants took advantage of the selenate mobility and presumably of the storage capacity of leaf vacuoles to circumvent selenium toxicity within the plant. Surprisingly, 28% of selenate was found in shoots of selenite-treated plants, questioning the ability of plants to oxidize selenite into selenate. Selenomethionine and methylated organo-selenium amounted to 30% and 8% respectively in shoots and 35% and 9% in roots of the identified Se, suggesting that selenium metabolization occurred concomitantly in root and shoot plant compartments and demonstrating that non-accumulator plants can synthesize notable quantities of precursor compound for volatilization. The present study demonstrated that non-accumulator plants can develop the same strategies as hyper-accumulator plants to limit selenium toxicity. When both selenate and selenite were supplied together, plants used selenate in a storage pathway and selenite in an assimilation pathway. Plants might thereby benefit from mixed supplies of selenite and selenate by saving enzymes and energy required for selenate reduction.

Current Knowledge on Genetic Biofortification in Lentil

Micronutrient deficiency in the human body, popularly known as "hidden hunger", causes many health problems. It presently affects >2 billion people worldwide, especially in South Asia and sub-Saharan Africa. Biofortification of food crop varieties is one way to combat the problem of hidden hunger using conventional plant breeding and transgenic methods. Lentils are rich sources of protein, micronutrients, and vitamins including iron, zinc, selenium, folates, and carotenoids. Lentil genetic resources including germplasm and wild species showed genetic variability for these traits. Studies revealed that a single serving of lentils could provide a significant amount of the recommended daily allowance of micronutrients and vitamins for adults. Therefore, lentils have been identified as a food legume for biofortification, which could provide a whole food solution to the global micronutrient malnutrition. The present review discusses the current ongoing efforts toward genetic biofortification in lentils using classical breeding and molecular marker-assisted approaches.

Selenium geochemical distribution in the environment and predicted human daily dietary intake in northeastern Qinghai, China

Ping'an is a selenium (Se)-rich region located in northeastern Qinghai Province of China. To better understand the selenium geochemical distribution and its potential ecological effects, this field study investigated the Se distribution in the local environment, soil Se bioavailability, and the daily dietary Se intake of Ping'an residents. Concentrations of total Se were determined in soil, plant, water, and food samples. Results showed that Ping'an is generally a Se-rich region in China. High-Se soil mainly distributes in the north of Hongshuiquan Town in the study region. Se concentration in 43 plant samples varied significantly from not detected (nd) to 904 μg/kg, following a descending order of pasture > grain > vegetable > fruit, which was much lower than other regions in China. The drinking water Se concentrations were also significantly lower than the European and Chinese surface water Se standards of 10 and 50 μg/L. The predicted daily dietary Se intake (48 ± 20 μg per person) in Ping'an met the demand of the WHO-recommended Se amount of 55 μg per person. The Se content is high in soil, but low in different kinds of plants and Se intake, indicating that Se that can be taken up by plants was very low. The K2HPO4-KH2PO4-extractable Se in the soil accounted for only 3% of the total soil Se, indicating that a low soil bioavailable Se might result in low Se accumulation in plant tissues in Ping'an. This might be due to the influences of geochemistry and the inherent properties of the parent materials of these soils. Therefore, further studies need to focus on better understanding the process and influential factors to soil Se bioavailability to successfully utilize the soil Se resource in low-Se-availability areas.

Synchrotron-based X-ray absorption near-edge spectroscopy imaging for laterally resolved speciation of selenium in fresh roots and leaves of wheat and rice

Knowledge of the distribution of selenium (Se) species within plant tissues will assist in understanding the mechanisms of Se uptake and translocation, but in situ analysis of fresh and highly hydrated plant tissues is challenging. Using synchrotron-based fluorescence X-ray absorption near-edge spectroscopy (XANES) imaging to provide laterally resolved data, the speciation of Se in fresh roots and leaves of wheat (Triticum aestivum L.) and rice (Oryza sativa L.) supplied with 1 μM of either selenate or selenite was investigated. For plant roots exposed to selenate, the majority of the Se was efficiently converted to C-Se-C compounds (i.e. methylselenocysteine or selenomethionine) as selenate was transported radially through the root cylinder. Indeed, even in the rhizodermis which is exposed directly to the bulk solution, only 12-31% of the Se was present as uncomplexed selenate. The C-Se-C compounds were probably sequestered within the roots, whilst much of the remaining uncomplexed Se was translocated to the leaves-selenate accounting for 52-56% of the total Se in the leaves. In a similar manner, for plants exposed to selenite, the Se was efficiently converted to C-Se-C compounds within the roots, with only a small proportion of uncomplexed selenite observed within the outer root tissues. This resulted in a substantial decrease in translocation of Se from the roots to leaves of selenite-exposed plants. This study provides important information for understanding the mechanisms responsible for the uptake and subsequent transformation of Se in plants.

Effects of selenite and selenate application on growth and shoot selenium accumulation of pak choi (Brassica chinensis L.) during successive planting conditions

Selenate and selenite are two main kinds of inorganic selenium (Se) sources in soil, but these substances can pose threats to the environment. Phytoextraction is an emerging technology to remove Se from polluted soils by using a hyper-accumulator. In this study, a pot experiment was conducted to investigate Se phytoextraction potential of pak choi (Brassica chinensis L.) and to determine the effects of Se on growth and Se accumulation of pak choi under successive planting conditions (four crops). Results showed that Se concentration in pak choi shoots significantly increased as selenate and selenite rates increased. Se concentration increased in successive crops on soil treated with selenite; by contrast, Se concentration decreased in crops on soil treated with selenate. Se concentrations of pak choi on soil treated with selenate were higher than those on soil treated with selenite. The maximum Se accumulations amount in crops on selenite- and selenate-treated soil were 7818 and 8828 μg · pot(-1), respectively. High bioconcentration factor (BCF) values indicated that pak choi could accumulate more Se from Se-contaminated soil. The Se phytoextraction efficiency of pak choi increased under successive planting conditions in selenite and selenate treatments; the maximum Se phytoextraction efficiencies of four successive crops of pak choi on selenite- and selenate-treated soil were 4.91 and 31.90 %, respectively. These differences between selenate and selenite treatments were attributed to the differences in Se forms in soil. Total and available Se contents in soil decreased significantly during repeated planting crops on soil treated with selenate; conversely, total and available Se contents decreased slightly in crops on soil treated with selenite. These results suggested that pak choi could highly tolerate and accumulate Se. Thus, pak choi may remove Se from contaminated soil; indeed, pak choi can be used in the phytoextraction of Se in polluted soil.

Distribution and accumulation of selenium in wild plants growing naturally in the Gumuskoy (Kutahya) mining area, Turkey

This study investigated selenium uptake and transport from the soil to 12 plant species in the mining area of Gumuskoy (Kutahya), Turkey. Plant samples and their associated soils were collected and analyzed for Se content by ICP-MS. Mean Se values in the soils, roots, and shoots of all plants were 0.9, 0.6, and 0.8 mg kg(-1), respectively. The mean enrichment coefficients for roots (ECR) and shoots (ECS) of these plants were 0.78 and 0.97. The mean translocation factors (TLF) were 1.33. These values indicate that all 12 plant species had the ability to transfer Se from the roots to the shoot, but that transfer was more efficient in plants with higher ECR and ECS. Therefore, these plants may be useful in phytoremediation in rehabilitating areas contaminated by Se because their ECR, ECS and TLFs are >1.

Review: The potential of the common bean (Phaseolus vulgaris) as a vehicle for iron biofortification

Common beans are a staple food and the major source of iron for populations in Eastern Africa and Latin America. Bean iron concentration is high and can be further increased by biofortification. A major constraint to bean iron biofortification is low iron absorption, attributed to inhibitory compounds such as phytic acid (PA) and polyphenol(s) (PP). We have evaluated the usefulness of the common bean as a vehicle for iron biofortification. High iron concentrations and wide genetic variability have enabled plant breeders to develop high iron bean varieties (up to 10 mg/100 g). PA concentrations in beans are high and tend to increase with iron biofortification. Short-term human isotope studies indicate that iron absorption from beans is low, PA is the major inhibitor, and bean PP play a minor role. Multiple composite meal studies indicate that decreasing the PA level in the biofortified varieties substantially increases iron absorption. Fractional iron absorption from composite meals was 4%–7% in iron deficient women; thus the consumption of 100 g biofortified beans/day would provide about 30%–50% of their daily iron requirement. Beans are a good vehicle for iron biofortification, and regular high consumption would be expected to help combat iron deficiency (ID).

Transformation of heavy metal fractions on soil urease and nitrate reductase activities in copper and selenium co-contaminated soil

This study aims to explore the effects of the distribution, transformation and bioavailability of different fractions of copper (Cu) and selenium (Se) in co-contaminated soils on soil enzymes, providing references for the phytoremediation of contaminated areas and agriculture environmental protection. Pot experiments and laboratory analysis were used to investigate the transformation and bioavailability of additional Cu and Se for pakchoi (Brassica chinensis) in co-contaminated soil. In the uncontaminated soil, Cu mainly existed in residual form, whereas Se was present in residual form and in elemental and organic-sulfide matter-bound form. In the contaminated soil, Cu mainly bound to Fe-Mn oxidates, whereas Se was in exchangeable and carbonates forms. After a month of pakchoi growth, Cu tended to transfer into organic matter-bound fractions, whereas Se tended to bound to Fe-Mn oxidates. The IR (reduced partition index) value of Cu decreased as the concentrations of Cu and Se gradually increased, whereas the IR value of Se decreased as the concentration of Se increased. The IR value before pakchoi planting and after it was harvested was not affected by the concentration of exogenous Cu. Soil urease and nitrate reductase activities were inhibited by Cu and Se pollution either individually or combined in different degrees, following the order nitrate reductase>urease. The significant correlation between the IR value and soil enzyme activities suggests that this value could be used to evaluate the bioavailability of heavy metals in soil. Path analysis showed that the variations in exchangeable Cu and organic-sulfide matter-bound and elemental Se had direct effects on the activities of the two enzymes, suggesting their high bioavailability. Therefore, the IR value and the transformation of metals in soil could be used as indicators in evaluating the bioavailability of heavy metals.