Enhanced selenium content in wheat grain by co-inoculation of selenobacteria and arbuscular mycorrhizal fungi: A preliminary study as a potential Se biofortification strategy

Effect of Rhodococcus opacus PD630 on selenium phytoremediation by Brassica oleracea

The purpose of this study was to evaluate the potential of microbial-enhanced Brassica oleracea for the phytoremediation of seleniferous soils. The effect of selenite (Se(IV)) and selenate (Se(VI)) on B. oleracea (1-100 mg.L-1) was examined through germination (7 d) and pot (30 d) trials. Microbial analysis was conducted to verify the toxic effect of various Se concentrations (1-500 mg.L-1) on Rhodococcus opacus PD360, and to determine if it exhibits plant growth promoter traits. R. opacus PD630 was found to tolerate high concentrations of both Se(IV) and Se(VI), above 100 mg.L-1. R. opacus PD630 reduced Se(IV) and Se(VI) over 7 days, with a Se conversion efficiency between 60 and 80%. Germination results indicated lower concentrations (0-10 mg.L-1) of Se(IV) and Se(VI) gave a higher shoot length (> 4 cm). B. oleracea accumulated 600-1,000 mg.kg-1 dry weight (DW) of Se(IV) and Se(VI), making it a secondary accumulator of Se. Moreover, seeds inoculated with R. opacus PD360 showed increased Se uptake (up to 1,200 mg Se.kg-1 DW). In addition, bioconcentration and translocation factors were greater than one. The results indicate a synergistic effect between R. opacus PD630 and B. oleracea for Se phytoextraction from polluted soils.

Exploring the potential of endophyte-plant interactions for improving crop sustainable yields in a changing climate

Climate change poses a major threat to global food security, significantly reducing crop yields as cause of abiotic stresses, and for boosting the spread of new and old pathogens and pests. Sustainable crop management as a route to mitigation poses the challenge of recruiting an array of solutions and tools for the new aims. Among these, the deployment of positive interactions between the micro-biotic components of agroecosystems and plants can play a highly significant role, as part of the agro-ecological revolution. Endophytic microorganisms have emerged as a promising solution to tackle this challenge. Among these, Arbuscular Mycorrhizal Fungi (AMF) and endophytic bacteria and fungi have demonstrated their potential to alleviate abiotic stresses such as drought and heat stress, as well as the impacts of biotic stresses. They can enhance crop yields in a sustainable way also by other mechanisms, such as improving the nutrient uptake, or by direct effects on plant physiology. In this review we summarize and update on the main types of endophytes, we highlight several studies that demonstrate their efficacy in improving sustainable yields and explore possible avenues for implementing crop-microbiota interactions. The mechanisms underlying these interactions are highly complex and require a comprehensive understanding. For this reason, omic technologies such as genomics, transcriptomics, proteomics, and metabolomics have been employed to unravel, by a higher level of information, the complex network of interactions between plants and microorganisms. Therefore, we also discuss the various omic approaches and techniques that have been used so far to study plant-endophyte interactions.

Effect of inoculation with arbuscular mycorrhizal fungi on the energy metabolism of selenite-rich amaranth

A series of pot trials were undertaken to examine the impact of four arbuscular mycorrhizal fungi (AMF), namely Glomus mosseae (G.m), Glomus etunicatum (G.e), Corymbiglomus tortuosum (C.t), and the combined application of Glomus etunicatum and Corymbiglomus tortuosum (G.e + C.t), on the energy metabolism of amaranth plants grown in soil enriched with selenite at a concentration of 0.5 mg kg-1 . The inoculation of four AMFs resulted in an increase in both amaranth biomass and selenium (Se) content in leaves. The activities of phosphoglucose isomerase (PGI) and glucose-6-phosphate dehydrogenase + 6-phosphogluconate dehydrogenase were observed to decrease when AMFs were inoculated, as compared with the absence of AMF inoculation. The inoculation with G.m, C.t, and G.e + C.t resulted in an increase in succinate dehydrogenase activity; however, the inoculation with G.m, G.e, and G.e + C.t led to an increase in ascorbate oxidase activity. Furthermore, the inoculation of all four AMFs resulted in an increase in cytochrome c oxidase activity and the concentrations of oxidized coenzyme I (NAD) and reduced coenzyme I (NADH). The polyphenol oxidase activity of amaranth plants increased when inoculated with G.m and G.e, whereas it decreased when inoculated with C.t and G.e + C.t. Furthermore, the application of all four AMF treatments resulted in a reduction in adenosine triphosphate (ATP) levels and energy charge. It was worth mentioning that there was a clear inverse relationship between the energy charge and the biomass, Se concentration in the leaves. The findings presented in this research indicated that AMF may have an impact on energy metabolism and ultimately the biomass of amaranth by influencing the uptake of Se.

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.

Biofortification revisited: Addressing the role of beneficial soil microbes for enhancing trace elements concentration in staple crops

Trace element deficiency is a pervasive issue contributing to malnutrition on a global scale. The primary cause of this hidden hunger is related to low dietary intake of essential trace elements, which is highly prevalent in numerous regions across the world. To address deficiency diseases in humans, fortification of staple crops with vital trace elements has emerged as a viable solution. Current methods for fortifying crops encompass chemical amendments, genetic breeding, and transgenic approaches, yet these approaches possess certain limitations, constraining their agricultural application. In contrast, fortifying staple crops through the utilization of soil-beneficial microbes has emerged as a promising and economically feasible approach to enhance trace element content in crops. A specific subset of these beneficial soil microbes, referred to as plant growth-promoting microbes, have demonstrated their ability to influence the interactions between plants, soil, and minerals. These microbes facilitate the transport of essential soil minerals, such as zinc, iron, and selenium, into plants, offering the potential for the development of tailored bioinoculants that can enhance the nutritional quality of cereals, pulses, and vegetable crops. Nevertheless, further research efforts are necessary to comprehensively understand the molecular mechanisms underlying the uptake, transport, and augmentation of trace element concentrations in staple crops. By delving deeper into these mechanisms, customized bioinoculants of soil-beneficial microbes can be developed to serve as highly effective strategies in combating trace element deficiency and promoting global nutritional well-being.

A Comparative Study of the Synthesis and Characterization of Biogenic Selenium Nanoparticles by Two Contrasting Endophytic Selenobacteria

The present study examined the biosynthesis and characterization of selenium nanoparticles (SeNPs) using two contrasting endophytic selenobacteria, one Gram-positive (Bacillus sp. E5 identified as Bacillus paranthracis) and one Gram-negative (Enterobacter sp. EC5.2 identified as Enterobacter ludwigi), for further use as biofortifying agents and/or for other biotechnological purposes. We demonstrated that, upon regulating culture conditions and selenite exposure time, both strains were suitable "cell factories" for producing SeNPs (B-SeNPs from B. paranthracis and E-SeNPs from E. ludwigii) with different properties. Briefly, dynamic light scattering (DLS), transmission electron microscopy (TEM), and atomic force microscopy (AFM) studies revealed that intracellular E-SeNPs (56.23 ± 4.85 nm) were smaller in diameter than B-SeNPs (83.44 ± 2.90 nm) and that both formulations were located in the surrounding medium or bound to the cell wall. AFM images indicated the absence of relevant variations in bacterial volume and shape and revealed the existence of layers of peptidoglycan surrounding the bacterial cell wall under the conditions of biosynthesis, particularly in the case of B. paranthracis. Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), energy-dispersive X-ray (EDS), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) showed that SeNPs were surrounded by the proteins, lipids, and polysaccharides of bacterial cells and that the numbers of the functional groups present in B-SeNPs were higher than in E-SeNPs. Thus, considering that these findings support the suitability of these two endophytic stains as potential biocatalysts to produce high-quality Se-based nanoparticles, our future efforts must be focused on the evaluation of their bioactivity, as well as on the determination of how the different features of each SeNP modulate their biological action and their stability.

Melanin Induction Restores the Pathogenicity of Gaeumannomyces graminis var. tritici in Wheat Plants

One of the most challenging aspects of long-term research based on microorganisms is the maintenance of isolates under ex situ conditions, particularly the conservation of phytopathological characteristics. Our research group has worked for more than 10 years with Gaumannomyces graminis var. tritici (Ggt), the main biotic factor affecting wheat. In this sense we preserved the microorganisms in oil overlaid. However, several strains preserved for a long time lost their pathogenicity. These strains show white and non-infective mycelia. In this sense, we hypothesized that this is attributable to low melanin content. Melanin is a natural pigment mainly involved in UV protection, desiccation, salinity, oxidation, and fungal pathogenicity. Therefore, understanding the melanin role on Ggt pathogenicity is fundamental to developing melanin activation strategies under laboratory studies. In this study, we induce melanin activation by UV-A light chamber, 320 to 400 nm (T1) and temperature changes of 30 °C, 15 °C, and 20 °C (T2). Fungal pathogenicity was evaluated by determination of blackening roots and Ggt was quantified by real-time PCR in inoculated wheat plants. Results revealed that Ggt grown under UV-A (T1) conditions showed around 40% higher melanin level with a concomitant effect on root infection (98% of blackened roots) and 4-fold more Ggt genome copy number compared with the control (non-infective mycelia) being T1, a more inductor factor compared with T2. These findings would support the role of melanin in pathogenicity in darkly pigmented fungi such as Ggt and could serve as a basis for activating pathogenicity under laboratory conditions.

Harnessing Native Bacillus spp. for Sustainable Wheat Production

The genus Bacillus has been widely applied in contemporary agriculture as an environmentally-friendly biological agent. However, the real effect of commercial Bacillus-based fertilizers and pesticides varies immensely in the field. To harness Bacillus for efficient wheat production, we reviewed the diversity, functionality, and applicability of wheat-associated native Bacillus for the first time. Our main findings are: (i) Bacillus spp. inhabit the rhizosphere, root, stem, leaf, and kernel of wheat; (ii) B. subtilis and B. velezensis are the most widely endophytic species that can be isolated from both below and aboveground tissues; (iii) major functions of these representative strains are promotion of plant growth and alleviation of both abiotic and biotic stresses in wheat; (iv) stability and effectiveness are 2 major challenges during field application; (v) a STVAE pipeline that includes 5 processes, namely, Screen, Test, Validation, Application, and Evaluation, has been proposed for the capture and refinement of wheat-associated Bacillus spp. In particular, this review comprehensively addresses possible solutions, concerns, and criteria during the development of native Bacillus-based inoculants for sustainable wheat production.

Biofortification: A long-term solution to improve global health- a review

Biofortification is a revolutionary technique for improving plant nutrition and alleviating human micronutrient deficiency. Fertilizers can help increase crop yield and growth, but applying too much fertilizer can be a problem because it leads to the release of greenhouse gases and eutrophication. One of the major global hazards that affects more than two million people globally is the decreased availability of micronutrients in food crops, which results in micronutrient deficiencies or "hidden hunger" in people. Micronutrients, like macronutrients, perform a variety of roles in plant and human nutrition. This review has highlighted the importance of micronutrients as well as their advantages. The uneven distribution of micronutrients in geological areas is not the only factor responsible for micronutrient deficiencies, other parameters including soil moisture, temperature, texture of the soil, and soil pH significantly affects the micronutrient concentration and their availability in the soil. To overcome this, different biofortification approaches are assessed in the review in which microbes mediated, Agronomic approaches, Plant breeding, and transgenic approaches are discussed. Hidden hunger can result in risky health conditions and diseases such as cancer, cardiovascular disease, osteoporosis, neurological disorders, and many more. Microbes-mediated biofortification is a novel and promising solution for the bioavailability of nutrients to plants in order to address these problems. Biofortification is cost effective, feasible, and environmentally sustainable. Bio-fortified crops boost our immunity, which helps us to combat these deadly viruses. The studies we discussed in this review have demonstrated that they can aid in the alleviation of hidden hunger.

Rhodotorula mucilaginosa CAM4 improved selenium uptake in Spinacia oleracea L. and soil enzymatic activities under abiotic stresses

This study aimed to examine selenium (Se) acquisition by spinach (Spinacia oleracea L.) plants growing under salinity and drought stress through the inoculation of Rhodotorula mucilaginosa strain CAM4. Under abiotic stress conditions, strain CAM4 with Se inoculation increased the shoot length, root length, shoot dry weight and root dry weight by 75.8-93.7%, 47.7-80.9%, 101.9-109.8% and 130.5-270.2%, respectively compared to uninoculated Se-treated plants grown under the same conditions. Under abiotic stresses, the Se-treated CAM4 inoculated plants showed a significant increase in Se concentration in the edible leaves of spinach, which was 227.3-234.5% higher than uninoculated Se-treated control plants. Likewise, strain CAM4 treatment significantly enhanced the plant nutrition of both micro and macro-nutrients. Under normal and abiotic stresses, CAM4 inoculation enhanced soil activities of acid phosphatase, alkaline phosphatase, dehydrogenase, β-glucosidase and urease in the post harvested soil up to 28-47.5%, 62.6-121.8%, 69-177.1%, 16.2-37.9% and 19.8-41.2%, respectively over corresponding uninoculated soil.

The role of nanoparticles in plant biochemical, physiological, and molecular responses under drought stress: A review

Drought stress (DS) is a serious challenge for sustaining global crop production and food security. Nanoparticles (NPs) have emerged as an excellent tool to enhance crop production under current rapid climate change and increasing drought intensity. DS negatively affects plant growth, physiological and metabolic processes, and disturbs cellular membranes, nutrient and water uptake, photosynthetic apparatus, and antioxidant activities. The application of NPs protects the membranes, maintains water relationship, and enhances nutrient and water uptake, leading to an appreciable increase in plant growth under DS. NPs protect the photosynthetic apparatus and improve photosynthetic efficiency, accumulation of osmolytes, hormones, and phenolics, antioxidant activities, and gene expression, thus providing better resistance to plants against DS. In this review, we discuss the role of different metal-based NPs to mitigate DS in plants. We also highlighted various research gaps that should be filled in future research studies. This detailed review will be an excellent source of information for future researchers to adopt nanotechnology as an eco-friendly technique to improve drought tolerance.

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.

Management of Rhizosphere Microbiota and Plant Production under Drought Stress: A Comprehensive Review

Drought generates a complex scenario worldwide in which agriculture should urgently be reframed from an integrative point of view. It includes the search for new water resources and the use of tolerant crops and genotypes, improved irrigation systems, and other less explored alternatives that are very important, such as biotechnological tools that may increase the water use efficiency. Currently, a large body of evidence highlights the role of specific strains in the main microbial rhizosphere groups (arbuscular mycorrhizal fungi, yeasts, and bacteria) on increasing the drought tolerance of their host plants through diverse plant growth-promoting (PGP) characteristics. With this background, it is possible to suggest that the joint use of distinct PGP microbes could produce positive interactions or additive beneficial effects on their host plants if their co-inoculation does not generate antagonistic responses. To date, such effects have only been partially analyzed by using single omics tools, such as genomics, metabolomics, or proteomics. However, there is a gap of information in the use of multi-omics approaches to detect interactions between PGP and host plants. This approach must be the next scale-jump in the study of the interaction of soil–plant–microorganism. In this review, we analyzed the constraints posed by drought in the framework of an increasing global demand for plant production, integrating the important role played by the rhizosphere biota as a PGP agent. Using multi-omics approaches to understand in depth the processes that occur in plants in the presence of microorganisms can allow us to modulate their combined use and drive it to increase crop yields, improving production processes to attend the growing global demand for food.

Selenium content and nutritional quality of Brassica chinensis L enhanced by selenium engineered nanomaterials: The role of surface charge

Selenium engineered nanomaterials (Se ENMs)-enabled agriculture has developed rapidly, however, the roles of surface charge in the bioavailability and enrichment efficiency of Se ENMs are still unknown. Herein, various Se ENMs of homogenous size (40-60 nm) and different surface charges (3.2 ± 0.7, -29.0 ± 0.4, and 45.5 ± 1.3 mV) were prepared to explore the Se content and nutritional quality in Brassica chinensis L. The results demonstrated that soil application of various Se ENMs (0.05 mg kg^-1) displayed different bio-availabilities via modulating the secretion of root exudates (e.g., tartaric, malic, and citric acids), microbial community composition (e.g., Flavobacterium, Pseudomonas, Paracoccus, Bacillus and Rhizobium) and root cell wall. Negatively charged Se ENMs (Se (-)) showed the highest Se content in the shoot of B. chinensis (3.7-folds). Se (-) also significantly increased yield (156.9%) and improved nutritional quality (e.g., ascorbic acid, amino acids, flavonoids, fatty acids, and tricarboxylic acid) of B. chinensis. Moreover, after harvest, the Se (-) did not lead to significant change in Se residue in soil, but the amount of Se residue in soil was increased by 5.5% after applying the traditional Se fertilizer (selenite). Therefore, this study provides useful information for producing Se-fortified agricultural products, while minimizing environmental risk.

Minerals solubilizing and mobilizing microbiomes: A sustainable approaches for managing minerals deficiency in agricultural soil

Agriculture faces challenges to fulfill the rising food demand due to shortage of arable land and various environmental stressors. Traditional farming technologies help in fulfilling food demand but they are harmful to humans and environmental sustainability. The food production along with agro-environmental sustainability could be achieved by encouraging farmers to use agro-environmental sustainable products such as biofertilizers and biopesticides consisting of live microbes or plant extract instead of chemical-based inputs. The ecofriendly formulations play a significant role in plant growth promotion, crop yield, and repairing degraded soil texture and fertility sustainably. Mineral solubilizing microbes that provide vital nutrients like phosphorus, potassium, zinc, and selenium are essential for plant growth and development and could be developed as biofertilizers. These microbes could be plant-associated (rhizospheric, endophytic, and phyllospheric) or inhabits the bulk soil, and diverse extreme habitats. Mineral solubilizing microbes from soil, extreme environments, surface and internal parts of the plant belong to diverse phyla such as Ascomycota, Actinobacteria, Basidiomycota, Bacteroidetes, Chlorobi, Cyanobacteria, Chlorophyta, Euryarchaeota, Firmicutes, Gemmatimonadetes, Mucoromycota, Proteobacteria, and Tenericutes. Mineral solubilizing microbes (MSMs) directly or indirectly stimulate plant growth and development either by releasing plant growth regulators; solubilizing phosphorus, potassium, zinc, selenium, and silicon; biological nitrogen fixation; and production of siderophores, ammonia, hydrogen cyanide, hydrolytic enzymes, and bioactive compound/secondary metabolites. Biofertilizer developed using mineral solubilizing microbes is an eco-friendly solution to the sustainable food production system in many countries worldwide. The present review deals with the biodiversity of mineral solubilizing microbes, and potential roles in crop improvement and soil well-being for agricultural sustainability.

Seleno-Amino Acids in Vegetables: A Review of Their Forms and Metabolism

Seleno-amino acids are safe, health-promoting compounds for humans. Numerous studies have focused on the forms and metabolism of seleno-amino acids in vegetables. Based on research progress on seleno-amino acids, we provide insights into the production of selenium-enriched vegetables with high seleno-amino acids contents. To ensure safe and effective intake of selenium, several issues need to be addressed, including (1) how to improve the accumulation of seleno-amino acids and (2) how to control the total selenium and seleno-amino acids contents in vegetables. The combined use of plant factories with artificial lighting and multiple analytical technologies may help to resolve these issues. Moreover, we propose a Precise Control of Selenium Content production system, which has the potential to produce vegetables with specified amounts of selenium and high proportions of seleno-amino acids.

The effect of arbuscular mycorrhizal fungi on the phenolic compounds profile, antioxidant activity and grain yields in wheat cultivars growing under hydric stress

BACKGROUND

Hydric stress affects the production of wheat (Triticum aestivum L.) worldwide, making some tools necessary to cope with the decrease in rainfall. A sustainable alternative is the use of arbuscular mycorrhizal fungi (AMF) as biofertilisers. Here, we analysed the effects of AMF strains adapted or non-adapted to hyper-arid conditions on the phenolic profiles and antioxidant activities of wheat grains from two cultivars with contrasting tolerance to osmotic stress (Ilustre, moderately tolerant; and Maxi, tolerant) grown with and without hydric stress.

RESULTS

Eight phenolic compounds were detected, apigenin-C-pentoside-C-hexoside I being the most abundant and showing an increase of 80.5% when inoculated with the fungus Funneliformis mosseae (FM) obtained from Atacama Desert under normal irrigation with respect to non-mycorrhizal (NM) plants. NM treatments were associated with higher grain yields. FM showed a noticeable effect on most phenolic compounds, with an increase up to 30.2% in apigenin-C-pentoside-C-hexoside III concentration under hydric stress with respect to normal irrigation, being also responsible for high antioxidant activities such as ABTS (2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) and DPPH (2,2-diphenyl-1-picrylhydrazyl) activities.

CONCLUSION

Inoculation with FM adapted to hydric stress produced improvements in phenolics composition and antioxidant activities in grains from wheat plants growing under hydric stress conditions, improving their food quality and supporting the development of further studies to determine whether the use of adapted AMF could be a realistic tool to improve grain quality in a scenario of increasing hydric stress conditions. © 2021 Society of Chemical Industry.

Interactions of nanoparticles and salinity stress at physiological, biochemical and molecular levels in plants: A review

Salinity stress is one of the most destructive non-biological stresses in plants that has adversely affected many agricultural lands in the world. Salinity stress causes many morphological, physiological, epigenetic and genetic changes in plants by increasing sodium and chlorine ions in the plant cells. The plants can alleviate this disorder to some extent through various mechanisms and return the cell to its original state, but if the salt dose is high, the plants may not be able to provide a proper response and can die due to salt stress. Nowadays, scientists have offered many solutions to this problem. Nanotechnology is one of the most emerging and efficient technologies that has been entered in this field and has recorded very brilliant results. Although some studies have confirmed the positive effects of nontechnology on plants under salinity stress, there is no the complete understanding of the relationship and interaction of nanoparticles and intracellular mechanisms in the plants. In the review paper, we have tried to reach a conclusion from the latest articles that how NPs could help salt-stressed plants to recover their cells under salt stress so that we can take a step towards clearing the existing ambiguities for researchers in this field.

Microbes: a potential tool for selenium biofortification

Selenium (Se) is a component of many enzymes and indispensable for human health due to its characteristics of reducing oxidative stress and enhancing immunity. Human beings take Se mainly from Se-containing crops. Taking measures to biofortify crops with Se may lead to improved public health. Se accumulation in plants mainly depends on the content and bioavailability of Se in soil. Beneficial microbes may change the chemical form and bioavailability of Se. This review highlights the potential role of microbes in promoting Se uptake and accumulation in crops and the related mechanisms. The potential approaches of microbial enhancement of Se biofortification can be summarized in the following four aspects: (1) microbes alter soil properties and impact the redox chemistry of Se to improve the bioavailability of Se in soil; (2) beneficial microbes regulate root morphology and stimulate the development of plants through the release of certain secretions, facilitating Se uptake in plants; (3) microbes upregulate the expression of certain genes and proteins that are related to Se metabolism in plants; and (4) the inoculation of microbes give rise to the generation of certain metabolites in plants contributing to Se absorption. Considering the ecological safety and economic feasibility, microbial enhancement is a potential tool for Se biofortification. For further study, the recombination and establishment of synthesis microbes is of potential benefit in Se-enrichment agriculture.

Fungal Mobilization of Selenium in the Presence of Hausmannite and Ferric Oxyhydroxides

Bioleaching of mineral phases plays a crucial role in the mobility and availability of various elements, including selenium. Therefore, the leachability of selenium associated with the surfaces of ferric and manganese oxides and oxyhydroxides, the prevailing components of natural geochemical barriers, has been studied in the presence of filamentous fungus. Both geoactive phases were exposed to selenate and subsequently to growing fungus Aspergillus niger for three weeks. This common soil fungus has shown exceptional ability to alter the distribution and mobility of selenium in the presence of both solid phases. The fungus initiated the extensive bioextraction of selenium from the surfaces of amorphous ferric oxyhydroxides, while the hausmannite (Mn₃O₄) was highly susceptible to biodeterioration in the presence of selenium. This resulted in specific outcomes regarding the selenium, iron, and manganese uptake by fungus and residual selenium concentrations in mineral phases as well. The adverse effects of bioleaching on fungal growth are also discussed.

Two new selenite reducing bacterial isolates from paddy soil and the potential Se biofortification of paddy rice

Selenium (Se) is an essential element for human health. Se-enriched agricultural products can promote people's intake of Se. Microorganisms play an important role in Se cycling. In this study, two new bacterial strains were isolated from paddy soil and were identified as Chitinophaga sp. and Comamonas testosteroni, respectively. More than 44% and 39% of 1.0 mM selenite were reduced in 84 h by them using yeast extract as carbon source, respectively. Scanning electron microscope (SEM) and Energy dispersive X-ray spectrometry (EDS) results indicated that the reduction product of selenite was nanometer Se. These strains could promote the available Se in soil and the content of Se in rice plants in pot experiments. Organic combined Se in soils was increased up to 35%, accompanied by the 92% and 130% increase of Se in rice plants. To our best knowledge, this is the first report of Se reduction by Chitinophaga. This work might provide a prospective strategy for microbial fortification of Se in corps.

Joint Biofortification of Plants with Selenium and Iodine: New Field of Discoveries

The essentiality of selenium (Se) and iodine (I) to human beings and the widespread areas of selenium and iodine deficiency determine the high significance of functional food production with high levels of these elements. In this respect, joint biofortification of agricultural crops with Se and I is especially attractive. Nevertheless, in practice this topic has raised many problems connected with the possible utilization of many Se and I chemical forms, different doses and biofortification methods, and the existence of wide species and varietal differences. The limited reports relevant to this subject and the multiplicity of unsolved questions urge the need for an adequate evaluation of the results obtained up-to-date, useful for developing further future investigations. The present review discusses the outcome of joint plant Se-I biofortification, as well as factors affecting Se and I accumulation in plants, paying special attention to unsolved issues. A particular focus has been given to the prospects of herb sprouts production enriched with Se and I, as well as the interactions between the latter microelements and arbuscular-mycorrhizal fungi (AMF).

Selenium Biofortification: Roles, Mechanisms, Responses and Prospects

The trace element selenium (Se) is a crucial element for many living organisms, including soil microorganisms, plants and animals, including humans. Generally, in Nature Se is taken up in the living cells of microorganisms, plants, animals and humans in several inorganic forms such as selenate, selenite, elemental Se and selenide. These forms are converted to organic forms by biological process, mostly as the two selenoamino acids selenocysteine (SeCys) and selenomethionine (SeMet). The biological systems of plants, animals and humans can fix these amino acids into Se-containing proteins by a modest replacement of methionine with SeMet. While the form SeCys is usually present in the active site of enzymes, which is essential for catalytic activity. Within human cells, organic forms of Se are significant for the accurate functioning of the immune and reproductive systems, the thyroid and the brain, and to enzyme activity within cells. Humans ingest Se through plant and animal foods rich in the element. The concentration of Se in foodstuffs depends on the presence of available forms of Se in soils and its uptake and accumulation by plants and herbivorous animals. Therefore, improving the availability of Se to plants is, therefore, a potential pathway to overcoming human Se deficiencies. Among these prospective pathways, the Se-biofortification of plants has already been established as a pioneering approach for producing Se-enriched agricultural products. To achieve this desirable aim of Se-biofortification, molecular breeding and genetic engineering in combination with novel agronomic and edaphic management approaches should be combined. This current review summarizes the roles, responses, prospects and mechanisms of Se in human nutrition. It also elaborates how biofortification is a plausible approach to resolving Se-deficiency in humans and other animals.

Combined use of arbuscular mycorrhizal fungus and selenium fertilizer shapes microbial community structure and enhances organic selenium accumulation in rice grain

Selenium (Se) deficiency is a public health concern that is mainly caused by inadequate intake of Se from staple crops. The purpose of this study is to investigate the effects of inoculation with different arbuscular mycorrhizal fungus (AMF) strains, including Funneliformis mosseae (Fm) and Glomus versiforme (Gv), and fertilization with selenite or selenate on the accumulation and speciation of Se in rice. The results showed that using both AMF inoculation and Se fertilization could promote organic Se accumulation in rice grain than using only Se fertilization. Moreover, grain of rice inoculated with Fm and grown in soil fertilized with selenate had the highest accumulation of Se, of which selenomethionine was the dominant Se species. The AMF inoculation also led to high content of available Se and high relative abundance of Firmicutes in soil. The high concentration of available Se in soil suggests that the AMF inoculation may modify the microbial community, which then causes the Se uptake of rice to increase, in turn causing the amount of organic Se accumulated in rice to increase. Based on these results, using AMF inoculation combined with Se fertilization can be a promising strategy for Se biofortification in rice.

Investigation of Different Selenium Sources and Supplying Methods for Selenium Enrichment of Basil Vegetable (A Case Study under Calcareous and Non-calcareous Soil Systems)

BACKGROUND

Selenium (Se) is a crucial component of selenoaminoacids and selenoproteins. Therefore, Se-enriched agricultural products can reduce health complications induced by Se deficiency.

OBJECTIVE

This research was carried out to investigate the effects of Se bio-enrichment on Basil grown in calcareous and non-calcareous soil systems and also to evaluate the changes in Se concentration in the soil after harvesting.

METHODS

The experiment executed in two calcareous and one non-calcareous soil systems, and different Se application methods (control, soil application, seed inoculation, foliar application, and soil + foliar application) were administered. Selenobacteria, a plant growth-promoting rhizobacteria (PGPR), derived from the soil was used as a biofertilizer, compared to the other Se sources.

RESULTS

The results showed that both soil types and the methods of Se application had significant effects (P ˂ 0.01) on root and shoot dry weights and concentrations of P, K, Zn, Fe, and Se in both of the root and shoot. Shoot dry weight of plants treated with foliar Se was maximum in the calcareous soil. Compared to the control treatment, foliar application of Se increased shoot Se content in both calcareous and non-calcareous soils by 242% and 204%, respectively. Furthermore, the increase in shoot Se concentration in calcareous soil induced by Se application increased the concentration of other nutrients in the shoot and root. Plant growth parameters and concentrations of nutrients were significantly increased by using selenobacter inoculum.

CONCLUSION

The application of Se-containing compounds can improve vegetable quality. Considering the daily requirement of the human body for minerals and nutrients, enriching basil with Se can play an important role in community health. Moreover, some patents have reported the effectiveness of endophyte bacteria.

Selenium Biofortification of Crop Food by Beneficial Microorganisms

Selenium (Se) is essential for human health, however, Se is deficient in soil in many places all around the world, resulting in human diseases, such as notorious Keshan disease and Keshin–Beck disease. Therefore, Se biofortification is a popular approach to improve Se uptake and maintain human health. Beneficial microorganisms, including mycorrhizal and root endophytic fungi, dark septate fungi, and plant growth-promoting rhizobacteria (PGPRs), show multiple functions, especially increased plant nutrition uptake, growth and yield, and resistance to abiotic stresses. Such functions can be used for Se biofortification and increased growth and yield under drought and salt stress. The present review summarizes the use of mycorrhizal fungi and PGPRs in Se biofortification, aiming to improving their practical use.

Prospects of Arbuscular Mycorrhizal Fungi Utilization in Production of Allium Plants

The need to improve crop yield and quality, decrease the level of mineral fertilizers and pesticides/herbicides supply, and increase plants' immunity are important topics of agriculture in the 21st century. In this respect, arbuscular mycorrhizal fungi (AMF) may be considered as a crucial tool in the development of a modern environmentally friendly agriculture. The efficiency of AMF application is connected to genetic peculiarities of plant and AMF species, soil characteristics and environmental factors, including biotic and abiotic stresses, temperature, and precipitation. Among vegetable crops, Allium species are particularly reactive to soil mycorrhiza, due to their less expanded root apparatus surface compared to most other species. Moreover, Allium crops are economically important and able to synthesize powerful anti-carcinogen compounds, such as selenomethyl selenocysteine and gamma-glutamyl selenomethyl selenocysteine, which highlights the importance of the present detailed discussion about the AMF use prospects to enhance Allium plant growth and development. This review reports the available information describing the AMF effects on the seasonal, inter-, and intra-species variations of yield, biochemical characteristics, and mineral composition of Allium species, with a special focus on the selenium accumulation both in ordinary conditions and under selenium supply.

Effects of Arbuscular Mycorrhizal Fungi on Yield, Biochemical Characteristics, and Elemental Composition of Garlic and Onion under Selenium Supply

Biofortification of garlic and onion plants with selenium and arbuscular mycorrhizal fungi inoculation are considered beneficial for producing functional food with anticarcinogenic properties. The effects of arbuscular mycorrhizal fungi (AMF) inoculation, sodium selenate foliar application, and the combination AMF + selenium (Se), compared to an untreated control, were assessed regarding the bulb yield, biochemical characteristics, and mineral composition. AMF + Se application resulted in the highest yield, monosaccharides, and Se content in both garlic and onion bulbs; and an increase of ascorbic acid and flavonoids in onion, and flavonoids in garlic. The highest bulb concentrations of P and K were recorded under the AMF + Se application, Ca was best affected by AMF, and Mg accumulation was highest under all the treatments in garlic and upon AMF + Se application in onion bulbs. Contrary to garlic, onion bulbs were characterized by a remarkable increase in microelements (B, Cu, Fe, Mn, Si, Zn) under the AMF + Se treatment. Selenium, either with or without AMF application, promoted the accumulation of B and Si in onion and Mo and Zn in garlic bulbs. It can be inferred that the interaction between AMF and Se is highly specific, differing for garlic and onion grown in similar environmental conditions in Grozny region, Chechen Republic.

Selenium biofortification in the 21st century: status and challenges for healthy human nutrition

BACKGROUND

Selenium (Se) is an essential element for mammals and its deficiency in the diet is a global problem. Plants accumulate Se and thus represent a major source of Se to consumers. Agronomic biofortification intends to enrich crops with Se in order to secure its adequate supply by people.

SCOPE

The goal of this review is to report the present knowledge of the distribution and processes of Se in soil and at the plant-soil interface, and of Se behaviour inside the plant in terms of biofortification. It aims to unravel the Se metabolic pathways that affect the nutritional value of edible plant products, various Se biofortification strategies in challenging environments, as well as the impact of Se-enriched food on human health.

CONCLUSIONS

Agronomic biofortification and breeding are prevalent strategies for battling Se deficiency. Future research addresses nanosized Se biofortification, crop enrichment with multiple micronutrients, microbial-integrated agronomic biofortification, and optimization of Se biofortification in adverse conditions. Biofortified food of superior nutritional quality may be created, enriched with healthy Se-compounds, as well as several other valuable phytochemicals. Whether such a food source might be used as nutritional intervention for recently emerged coronavirus infections is a relevant question that deserves investigation.

Comparative de novo transcriptomics and untargeted metabolomic analyses elucidate complicated mechanisms regulating celery (Apium graveolens L.) responses to selenium stimuli

Presently, concern regarding the effects of selenium (Se) on the environment and organisms worldwide is increasing. Too much Se in the soil is harmful to plants. In this study, Illumina RNA sequencing and the untargeted metabolome of control and Se-treated celery seedlings were analyzed. In total, 297,911,046 clean reads were obtained and assembled into 150,218 transcripts (50,876 unigenes). A total of 36,287 unigenes were annotated using different databases. Additionally, 8,907 differentially expressed genes, including 5,319 up- and 3,588 downregulated genes, were identified between mock and Se-treated plants. “Phenylpropanoid biosynthesis” was the most enriched KEGG pathway. A total of 24 sulfur and selenocompound metabolic unigenes were differentially expressed. Furthermore, 1,774 metabolites and 237 significant differentially accumulated metabolites were identified using the untargeted metabolomic approach. We conducted correlation analyses of enriched KEGG pathways of differentially expressed genes and accumulated metabolites. Our findings suggested that candidate genes and metabolites involved in important biological pathways may regulate Se tolerance in celery. The results increase our understanding of the molecular mechanism responsible for celery’s adaptation to Se stress.

A Review of Studies from the Last Twenty Years on Plant–Arbuscular Mycorrhizal Fungi Associations and Their Uses for Wheat Crops

The aim of this work was to summarize the most recent research focused on the study of plant–arbuscular mycorrhizal fungi (AMF) symbiosis, both in a generic context and in the specific context of wheat cultivation. Taking into account the last 20 years, the most significant studies on the main plant advantages taken from this association are reviewed herein. Positive advances that have been reported stem from the mutualistic relationship between the plant and the mycorrhizal fungus, revealing better performance for the host in terms of nutrient uptake and protection from salinity, lack of water, and excess phytotoxic elements. Mycorrhiza studies and the recent progress in research in this sector have shown a possible solution for environmental sustainability: AMF represent a valid alternative to overcome the loss of biological fertility of soils, reduce chemical inputs, and alleviate the effects of biotic and abiotic stress.

Effect of Selenium Biofortification and Beneficial Microorganism Inoculation on Yield, Quality and Antioxidant Properties of Shallot Bulbs

Plant biofortification with selenium in interaction with the application of an arbuscular mycorrhizal fungi (AMF)-based formulate, with the goal of enhancing Se bioavailability, is beneficial for the development of the environmentally friendly production of functional food with a high content of this microelement. Research was carried out in order to assess the effects of an AMF-based formulate and a non-inoculated control in factorial combination with two selenium treatments with an organic (selenocystine) or inorganic form (sodium selenate) and a non-treated control on the yield, quality, antioxidant properties, and elemental composition of shallot (Allium cepa L. Aggregatum group). Selenocystine showed the best effect on the growth and yield of mycorrhized plants, whereas sodium selenate was the most effective on the non-inoculated plants. The soluble solids, total sugars, monosaccharides, titratable acidity, and proteins attained higher values upon AMF inoculation. Sodium selenate resulted in higher soluble solids, total sugars and monosaccharide content, and titratable acidity than the non-treated control, and it also resulted in higher monosaccharides when compared to selenocystine; the latter showed higher protein content than the control. Calcium, Na, S, and Cl bulb concentrations were higher in the plants inoculated with the beneficial microorganisms. Calcium and sodium concentrations were higher in the bulbs of plants treated with both the selenium forms than in the control. Selenocystine-treated plants showed enhanced accumulation of sulfur and chlorine compared to the untreated plants. The AMF inoculation increased the bulb selenium content by 530%, and the Se biofortification with selenocystine and sodium selenate increased this value by 36% and 21%, respectively, compared to control plants. The AMF-based formulate led to increases in ascorbic acid and antioxidant activity when compared to the non-inoculated control. The bulb ascorbic acid was increased by fortification with both selenium forms when compared to the non-treated control. The results of our investigation showed that both AMF and selenium application represent environmentally friendly strategies to enhance the overall yield and quality performances of shallot bulbs, as well as their selenium content.

Genotypic Variation and Biofortification with Selenium in Brazilian Wheat Cultivars

Selenium is essential to human and animal health, as it regulates glutathione peroxidase activity. Although not considered essential to plants, it may be beneficial to plant growth and development at low concentrations. This study evaluated the effect of selenate application on Se biofortification, macro- and micronutrient content, and the expression of genes involved in Se uptake and assimilation in 12 Brazilian wheat ( L.) cultivars. This nutrient-solution experiment was performed in a greenhouse and consisted of a complete 12 × 2 factorial randomized design, with 12 wheat cultivars in the absence or presence of Se in solution (13 μmol), with three replicates. The presence of Se in solution did not affect growth and yield of wheat cultivars. Selenium content and accumulation in the grain varied significantly among the different cultivars. The presence of Se affected macronutrient content more than micronutrient content, and selenate application increased S content in the shoots of eight cultivars and in the grains of five cultivars. Examination of gene expression did not allow identification of responses within the two groups of cultivars-with high or low Se contents-after selenate application. Our findings are relevant to the design of Se biofortification strategies for wheat in tropical and subtropical agroecosystems.

Use of plant growth promoting rhizobacteria (PGPRs) with multiple plant growth promoting traits in stress agriculture: Action mechanisms and future prospects

Increased incidence of abiotic stresses impacting adversely plant growth and productivity in major crops is being witnessed all over the world. Therefore, as a result of such stress factors, plant growth under the stress conditions will be less than the non-stress conditions. Growing concerns and global demand for correct, environmentally-friendly techniques exist to reduce the adverse effects of plant stress. Under such stressful conditions, the role of interactions of plant and beneficial microorganisms is of great significance. Application of plant growth promoting rhizobacteria (PGPRs) is a useful option to decrease these stresses and is now widely in practice. Plants inoculated with PGPRs induce morphological and biochemical modifications resulting in increased tolerance to abiotic stresses defined as IST (induced systemic tolerance). PGPRs increase plant growth and resistance to abiotic stresses through various mechanisms (more than one mechanism of action) such as production of ACC (1-aminocyclopropane-1-carboxylate) deaminase, reducing production of stress ethylene, modifications in phytohormonal content, induction of synthezing plant antioxidative enzymes, improvement in the uptake of essential mineral elements, extracellular polymeric substance (EPS) production, decrease in the absorbtion of excess nutrients/heavy metals, and induction of abiotic stress resistance genes. Experimental evidence also suggests that stimulated plant growth by these bacteria is the net result of various mechanisms of action that are activated simultaneously. In this review paper, we reviewed the action mechanisms through which PGPRs could alleviate abiotic stresses (salinity, drought, heavy metal toxicity, and nutritional imbalance) in plants. Use of PGPRs is predicted to become a suitable strategy and an emerging trend in sustainable enhancement of plant growth. Generally, ACC deaminase and IAA-producing bacteria can be a good option for optimal crop production and production of bio-fertilizers in the future due to having multiple potentials in alleviating stresses of salinity, drought, nutrient imbalance, and heavy metals toxicity in plants. This review paper also emphasizes future research needs about the combined utilization of stress tolerant-PGPRs with multiple plant growth promoting (PGP) characteristics under environmental stresses.

An Overview of Selenium Uptake, Metabolism, and Toxicity in Plants

Selenium (Se) is an essential micronutrient for humans and animals, but lead to toxicity when taken in excessive amounts. Plants are the main source of dietary Se, but essentiality of Se for plants is still controversial. However, Se at low doses protects the plants from variety of abiotic stresses such as cold, drought, desiccation, and metal stress. In animals, Se acts as an antioxidant and helps in reproduction, immune responses, thyroid hormone metabolism. Selenium is chemically similar to sulfur, hence taken up inside the plants via sulfur transporters present inside root plasma membrane, metabolized via sulfur assimilatory pathway, and volatilized into atmosphere. Selenium induced oxidative stress, distorted protein structure and function, are the main causes of Se toxicity in plants at high doses. Plants can play vital role in overcoming Se deficiency and Se toxicity in different regions of the world, hence, detailed mechanism of Se metabolism inside the plants is necessary for designing effective Se phytoremediation and biofortification strategies.

Minimal ecosystem uptake of selenium from Westland petrels, a forest-breeding seabird

Endemic Westland petrels (Procellaria westlandica) are a remnant of extensive seabird populations that occupied the forested hill country of prehuman New Zealand. Because seabird guano is rich in Se, an often-deficient essential element, we proposed that Westland petrels enhance Se concentrations in ecosystems associated with their breeding grounds. We sampled terrestrial (soil, plants, riparian spiders) and freshwater (benthic invertebrates, fish) components from Westland petrel-enriched and non-seabird forests on the western coast of New Zealand's South Island, an area characterised by highly leached, nutrient-poor soils. Median seabird soil Se was an order of magnitude higher than soil from non-seabird sites (2.2mgkg^-1 compared to 0.2mgkg^-1), but corresponding plant foliage concentrations (0.06mgkg^-1; 0.05mgkg^-1) showed no difference between seabird and non-seabird sites. In streams, Se ranged from 0.05mgkg^-1 (riparian foliage) to 3.1mgkg^-1 (riparian spiders and freshwater mussels). However, there was no difference between seabird and non-seabird streams. Stoichiometric ratios (N:Se, P:Se) showed Se loss across all ecosystem components relative to seabird guano, except in seabird colony soil where N was lost preferentially. Seabirds therefore did not enrich the terrestrial plants and associated stream ecosystems in Se. We conclude that incorporation of trace elements brought ashore by seabirds cannot be assumed, even though seabirds are a significant source of marine-derived nutrients and trace elements to coastal ecosystems world-wide.

Biofortification and phytoremediation of selenium in China

Selenium (Se) is an essential trace element for humans and animals but at high concentrations, Se becomes toxic to organisms due to Se replacing sulfur in proteins. Selenium biofortification is an agricultural process that increases the accumulation of Se in crops, through plant breeding, genetic engineering, or use of Se fertilizers. Selenium phytoremediation is a green biotechnology to clean up Se-contaminated environments, primarily through phytoextraction and phytovolatilization. By integrating Se phytoremediation and biofortification technologies, Se-enriched plant materials harvested from Se phytoremediation can be used as Se-enriched green manures or other supplementary sources of Se for producing Se-biofortified agricultural products. Earlier studies primarily aimed at enhancing efficacy of phytoremediation and biofortification of Se based on natural variation in progenitor or identification of unique plant species. In this review, we discuss promising approaches to improve biofortification and phytoremediation of Se using knowledge acquired from model crops. We also explored the feasibility of applying biotechnologies such as inoculation of microbial strains for improving the efficiency of biofortification and phytoremediation of Se. The key research and practical challenges that remain in improving biofortification and phytoremediation of Se have been highlighted, and the future development and uses of Se-biofortified agricultural products in China has also been discussed.

Microbial-enhanced Selenium and Iron Biofortification of Wheat (Triticum aestivum L.)--Applications in Phytoremediation and Biofortification

Selenium (Se) is an essential trace element for humans and other mammals. Most dietary Se is derived from crops. To develop a Se biofortification strategy for wheat, the effect of selenate fertilization and bacterial inoculation on Se uptake and plant growth was investigated. YAM2, a bacterium with 99% similarity to Bacillus pichinotyi, showed many plant growth promoting characteristics. Inoculation with YAM2 enhanced wheat growth, both in the presence and absence of selenate: YAM2-inoculated plants showed significantly higher dry weight, shoot length and spike length compared to un-inoculated plants. Selenate also stimulated wheat growth; Un-inoculated Se-treated plants showed a significantly higher dry weight and shoot length compared to control plants without Se. Bacterial inoculation significantly enhanced Se concentration in wheat kernels (167%) and stems (252%), as well as iron (Fe) levels in kernels (70%) and stems (147%), compared to un-inoculated plants. Inoculated Se-treated plants showed a significant increase in acid phosphatase activity, which may have contributed to the enhanced growth. In conclusion; Inoculation with Bacillus sp. YAM2 is a promising Se biofortification strategy for wheat and potentially other crops.

Characterization of selenium-enriched wheat by agronomic biofortification

Agronomic biofortification of staple crops is an effective way to enhance their contents in essential nutrients up the food chain, with a view to correcting for their deficiencies in animal or human status. Selenium (Se) is one such case, for its uneven distribution in the continental crust and, therefore, in agricultural lands easily translates into substantial variation in nutritional intakes. Cereals are far from being the main sources of Se on a content basis, but they are likely the major contributors to intake on a dietary basis. To assess their potential to assimilate and biotransform Se, bread and durum wheat were enriched with Se through foliar and soil addition at an equivalent field rate of 100 g of Se per hectare (ha), using sodium selenate and sodium selenite as Se-supplementation matrices, in actual field conditions throughout. Biotransformation of inorganic Se was evaluated by using HPLC-ICP-MS after enzymatic hydrolysis for Se-species extraction in the resulting mature wheat grains. Selenomethionine and Se(VI) were identified and quantified: the former was the predominant species, representing 70-100 % of the total Se in samples; the maximum amount of inorganic Se was below 5 %. These results were similar for both supplementation methods and for both wheat varieties. Judging from the present results, one can conclude that agronomic biofortification of wheat may improve the nutritional quality of wheat grains with significant amounts of selenomethionine, which is an attractive option for increasing the Se status in human diets through Se-enriched, wheat-based foodstuff.