Selenium as a potential fungicide could protect oilseed rape leaves from Sclerotinia sclerotiorum infection

Exploring the mechanism of nano-selenium treatment on the nutritional quality and resistance in plum plants

The impact of emerging stressors, such as pesticides and heavy metals, on the nutritional quality, resistance, and antioxidant systems of crops is the subject of intense monitoring. Due to its low toxicity and biocompatibility, nano-selenium (nano-Se) increases antioxidant capacity more effectively than selenium (Se). However, the protective mechanism of nano-Se in plum trees is still unknown when subjected to long-term abiotic stress. In this study, nano-Se foliar application enhanced the fruit's fresh weight and diameter and plant growth and development by increasing the content of trace elements (Zn and Se) and amino acids (Try, Phe, Pro, and Arg) in leaves and fruits. Compared to the control, nano-Se treatment dramatically improved the plant's antioxidant system, resulting in a substantial increase in SOD (44.3 %), POD (24.3 %), and CAT (95.6 %) levels. It also increased IAA (118.8 %), total flavonoids (23.0 %), total phenols (15.8 %), rutin (37.7 %), quercetin (146.8 %), and caffeic acid (19.8 %) contents by regulating phenylpropane metabolic pathways. Targeted amino acid analysis indicated that nano-Se biofortification greatly enhanced the levels of His (60.7 %), Ser (123.5 %), Thr (105.7 %), Val (202.1 %), Ile (236.2 %), Leu (84.0 %), Tyr (235.0 %), and Phe (164.7 %). The non-target metabolomics results showed that nano-Se treatment stimulated plum growth and nutrition by boosting phenylpropane metabolism and amino acid production. Therefore, nano-Se can improve the quality and resistance of plums by regulating both the primary and secondary metabolic pathways of plants and enhancing the antioxidant capacity. This investigation provides a reference for extrapolating the positive effects of nano-Se on crop quality to other plant species.

Selenium in soil enhances resistance of oilseed rape to Sclerotinia sclerotiorum by optimizing the plant microbiome

Plants can recruit beneficial microbes to enhance their ability to resist disease. It is well established that selenium is beneficial in plant growth, but its role in mediating microbial disease resistance remains poorly understood. Here, we investigated the correlation between selenium, oilseed rape rhizosphere microbes, and Sclerotinia sclerotiorum. Soil application of 0.5 and 1.0 mg kg-1 selenium [selenate Na2SeO4, Se(VI) or selenite Na2SeO3, Se(IV)] significantly increased the resistance of oilseed rape to Sclerotinia sclerotiorum compared with no selenium application, with a disease inhibition rate higher than 20% in Se(VI)0.5, Se(IV)0.5 and Se(IV)1.0 mg kg-1 treatments. The disease resistance of oilseed rape was related to the presence of rhizosphere microorganisms and beneficial bacteria isolated from the rhizosphere inhibited Sclerotinia stem rot. Burkholderia cepacia and the synthetic community consisting of Bacillus altitudinis, Bacillus megaterium, Bacillus cereus, Bacillus subtilis, Bacillus velezensis, Burkholderia cepacia, and Flavobacterium anhui enhanced plant disease resistance through transcriptional regulation and activation of plant-induced systemic resistance. In addition, inoculation of isolated bacteria optimized the bacterial community structure of leaves and enriched beneficial microorganisms such as Bacillus, Pseudomonas, and Sphingomonas. Bacillus isolated from the leaves were sprayed on detached leaves, and it also performed a significant inhibition effect on Sclerotinia sclerotiorum. Overall, our results indicate that selenium improves plant rhizosphere microorganisms and increase resistance to Sclerotinia sclerotiorum in oilseed rape.

Nano-Selenium and Glutathione Enhance Cucumber Resistance to Botrytis cinerea by Promoting Jasmonic Acid-Mediated Cucurbitacin Biosynthesis

Nano-selenium (Nano-Se), as a biological stimulant, promotes plant growth and development, as well as defense against biotic and abiotic stresses. Glutathione (GSH) is a crucial antioxidant and is also involved in the plant defense response to various stresses. In this study, the efficacy of combined treatment of Nano-Se and GSH (SeG) on the resistance of cucumber plants to Botrytis cinerea was investigated in terms of the plant phenotype, gene expression, and levels of accumulated metabolites using transcriptomic and metabolomic analyses. The exogenous application of SeG significantly enhanced plant growth and increased photosynthetic pigment contents and capacity. Notably, B. cinerea infection was reduced markedly by 41.9% after SeG treatment. At the molecular level, the SeG treatment activated the alpha-linolenic acid metabolic pathway and upregulated the expression of genes responsible for jasmonic acid (JA) synthesis, including LOX (210%), LOX4 (430%), AOS1 (100%), and AOC2 (120%), therefore promoting JA accumulation in cucumber. Intriguingly, the level of cucurbitacin, an important phytoalexin in cucurbitaceous plants, was found to be increased in SeG-treated cucumber plants, as was the expression of cucurbitacin biosynthesis-related genes OSC (107.5%), P450 (440.8%,31.6%), and ACT (414.0%). These genes were also upregulated by JA treatment, suggesting that JA may be an upstream regulator of cucurbitacin biosynthesis. Taken together, this study demonstrated that pretreatment of cucumber plants with SeG could activate the JA signaling pathway and promote cucurbitacin biosynthesis to enhance the resistance of the plants to B. cinerea infection. The findings also indicate that SeG is a promising biostimulant for protecting cucumber plants from B. cinerea infection without growth loss.

Maleic acid and malonic acid reduced the pathogenicity of Sclerotinia sclerotiorum by inhibiting mycelial growth, sclerotia formation and virulence factors

Sclerotinia sclerotiorum is a necrotrophic plant pathogenic fungus with broad distribution and host range. Bioactive compounds derived from plant extracts have been proven to be effective in controlling S. sclerotiorum. In this study, the mycelial growth of S. sclerotiorum was effectively inhibited by maleic acid, malonic acid, and their combination at a concentration of 2 mg/mL, with respective inhibition rates of 32.5%, 9.98%, and 67.6%. The treatment of detached leaves with the two acids resulted in a decrease in lesion diameters. Interestingly, maleic acid and malonic acid decreased the number of sclerotia while simultaneously increasing their weight. The two acids also disrupted the cell structure of sclerotia, leading to sheet-like electron-thin regions. On a molecular level, maleic acid reduced oxalic acid secretion, upregulated the expression of Ss-Odc2 and downregulated CWDE10, Ss-Bi1 and Ss-Ggt1. Differently, malonic acid downregulated CWDE2 and Ss-Odc1. These findings verified that maleic acid and malonic acid could effectively inhibit S. sclerotiorum, providing promising evidence for the development of an environmentally friendly biocontrol agent.

Nano-selenium enhances melon resistance to Podosphaera xanthii by enhancing the antioxidant capacity and promoting alterations in the polyamine, phenylpropanoid and hormone signaling pathways

Powdery mildew is one of the main problematic diseases in melon production, requiring the use of chemical pesticides with disease-resistant cultivars for control. However, the often rapid acquisition of fungicidal resistance by mildew pathogens makes this practice unsustainable. The identification of crop treatments that can enhance resistance to powdery mildew resistance is therefore important to reduce melon crop attrition. This study indicates that the application of Nano-Se can reduce the powdery mildew disease index by 21-45%. The Nano-Se treatment reduced reactive oxygen species (ROS) and malondialdehyde (MDA) accumulation, with increases in glutathione (GSH), proline and 1,1-Diphenyl-2-picrylhydrazyl radical (DPPH). Increases were also observed in the activities and transcriptional levels of the antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX) and peroxidase (POD). Assays with four different cultivars of melon with differing levels of mildew resistance demonstrated that relative to the control, the Nano-Se treatment resulted in larger responses to mildew infection, including increases in the levels of putrescine (PUT; 43-112%) and spermine (SPM; 36-118%), indoleacetic acid (IAA; 43-172%) and salicylic acid (SA; 24-73%), the activities of phenylalanine ammonium lyase (PAL), trans-cinnamate 4-hydroxylase (C4H) and 4-coumarate: Co A ligase (4CL) of the phenylpropanoid pathway (22-38%, 24-126% and 19-64%, respectively). Key genes in the polyamine and phenylpropanoid pathway were also upregulated. These results indicate that the foliar application of Nano-Se improved melon defenses against powdery mildew infection, with a significant reduction in mildew disease development.

Review on Pesticide Abiotic Stress over Crop Health and Intervention by Various Biostimulants

Plants are essential for life on earth, and agricultural crops are a primary food source for humans. For the One Health future, crop health is crucial for safe, high-quality agricultural products and the development of future green commodities. However, the overuse of pesticides in modern agriculture raises concerns about their adverse effects on crop resistance and product quality. Recently, biostimulants, including microecological bacteria agents and nanoparticles, have garnered worldwide interest for their ability to sustain plant health and enhance crop resistance. This review analyzed the effects and mechanisms of pesticide stress on crop health. It also investigated the regulation of biostimulants on crop health and the multiomics mechanism, combining research on nanoselenium activating various crop health aspects conducted by the authors' research group. The paper helps readers understand the impact of pesticides on crop health and the positive influence of various biostimulants, especially nanomaterials and small molecules, on crop health.

Nano-selenium enhances sugarcane resistance to Xanthomonas albilineans infection and improvement of juice quality

Selenium is an important trace element that is beneficial to human health and can enhance plant resistance and crop quality. The occurrence of up-to-date nanotechnology greatly promotes the beneficial efficiency of this trace element on crops. The discovery of nano-Se increased the crop quality and reduced plant disease in different plant. In this study, we reduced sugarcane leaf scald disease incidence by exogenously spraying different concentrations (5 mg/L and 10 mg/L) of nano-Se. Additional studies revealed that spraying of nano-Se reduced reactive oxygen species (ROS) and H₂O₂ accumulation, and increased antioxidant enzyme activities in sugarcane. The nano-selenium treatments also increased the content of jasmonic acid (JA) and the expression of JA pathway genes. Furthermore, we also found that use nano-Se treatment in an appropriate way can enhance the quality of cane juice. The brix of the cane juice of the selenium-enriched treatment was significantly higher than that of the control group, which was 10.98% and 20.81% higher than that of the CK group, respectively. Meanwhile, the content of certain beneficial amino acids was increased, with the highest being 3.9 times higher than the control. Taken together, our findings inferred that nano-Se could act as a potential eco-fungicide to protect sugarcane from can be used as a potential ecological bactericide to protect sugarcane from Xanthomonas albilineans infections, and improve sugarcane quality. The results arising from this study not only introduces an ecological method to control X. albilineans, but also provides a deep insight into this trace elements for improving juice quality.

The use of selenium for controlling plant fungal diseases and insect pests

The selenium (Se) applications in biomedicine, agriculture, and environmental health have become great research interest in recent decades. As an essential nutrient for humans and animals, beneficial effects of Se on human health have been well documented. Although Se is not an essential element for plants, it does play important roles in improving plants' resistances to a broad of biotic and abiotic stresses. This review is focused on recent findings from studies on effects and mechanisms of Se on plant fungal diseases and insect pests. Se affects the plant resistance to fungal diseases by preventing the invasion of fungal pathogen through positively affecting plant defense to pathogens; and through negative effects on pathogen by destroying the cell membrane and cellular extensions of pathogen inside plant tissues after invasion; and changing the soil microbial community to safeguard plant cells against invading fungi. Plants, grown under Se enriched soils or treated with Se through foliar and soil applications, can metabolize Se into dimethyl selenide or dimethyl diselenide, which acts as an insect repellent compound to deter foraging and landing pests, thus providing plant mediated resistance to insect pests; moreover, Se can also lead to poisoning to some pests if toxic amounts of Se are fed, resulting in steady pest mortality, lower reproduction rate, negative effects on growth and development, thus shortening the life span of many insect pests. In present manuscript, reports are reviewed on Se-mediated plant resistance to fungal pathogens and insect pests. The future perspective of Se is also discussed on preventing the disease and pest control to protect plants from economic injuries and damages.

Nano-selenium enhances the antioxidant capacity, organic acids and cucurbitacin B in melon (Cucumis melo L.) plants

Pesticides are widely used in melon production causing safety issues around the consumption of melon and increasing pathogen and insect tolerance to pesticides. This study investigated whether a nano-selenium (Nano-Se) spray treatment can improve resistance to biological stress in melon plants, reducing the need for pesticides, and how this mechanism is activated. To achieve this, we examine the ultrastructure and physio-biochemical responses of two melon cultivars after foliar spraying with Nano-Se. Nano-Se treatment reduced plastoglobulins in leaf mesophyll cells, thylakoid films were left intact, and compound starch granules increased. Nano-Se treatment also increased root mitochondria and left nucleoli intact. Nano-Se treatment enhanced ascorbate peroxidase, peroxidase, phenylalanine ammonia lyase, β-1,3-glucanase, chitinase activities and their mRNA levels in treated melon plants compared to control plants (without Nano-Se treatments). Exogenous application of Nano-Se improved fructose, glucose, galactitol, stachyose, lactic acid, tartaric acid, fumaric acid, malic acid and succinic acid in treated plants compared to control plants. In addition, Nano-Se treatment enhanced cucurbitacin B and up-regulated eight cucurbitacin B synthesis-related genes. We conclude that Nano-Se treatment of melon plants triggered antioxidant capacity, photosynthesis, organic acids, and up-regulated cucurbitacin B synthesis-related genes, which plays a comprehensive role in stress resistance in melon plants.

Synergistic Effect of Melatonin and Selenium Improves Resistance to Postharvest Gray Mold Disease of Tomato Fruit

Melatonin (MT) is a ubiquitous hormone molecule that is commonly distributed in nature. MT not only plays an important role in animals and humans but also has extensive functions in plants. Selenium (Se) is an essential micronutrient for animals and humans, and is a beneficial element in higher plants at low concentrations. Postharvest diseases caused by fungal pathogens lead to huge economic losses worldwide. In this study, tomato fruits were treated with an optimal sodium selenite (20 mg/L) and melatonin (10 μmol/L) 2 h and were stored for 7 days at room temperature simulating shelf life, and the synergistic effects of Se and MT collectively called Se-Mel on gray mold decay in tomato fruits by Botrytis cinerea was investigated. MT did not have antifungal activity against B. cinerea in vitro, while Se significantly inhibited gray mold development caused by B. cinerea in tomatoes. However, the interaction of MT and Se showed significant inhibition of the spread and growth of the disease, showing the highest control effect of 74.05%. The combination of MT with Se treatment enhanced the disease resistance of fruits by improving the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), as well as increasing the gene expression level of pathogenesis-related (PR) proteins. Altogether, our results indicate that the combination of MT and Se would induce the activation of antioxidant enzymes and increase the expression of PR proteins genes that might directly enhance the resistance in tomato fruit against postharvest pathogenic fungus B. cinerea.

Nanoselenium Enhanced Wheat Resistance to Aphids by Regulating Biosynthesis of DIMBOA and Volatile Components

The mechanism of nanoselenium (nano-Se) improving the resistance induced by plant components to aphids is unclear. In this study, foliar sprayed nano-Se (5.0 mg/L) could significantly reduce the Sitobion avenae number (36%) compared with that in the control. Foliar application of nano-Se enhanced the antioxidant capacity by reducing malondialdehyde (MDA) and increasing GSH-Px, CAT, GSH, Pro, and VE concentrations in wheat seedlings. The phenylpropane pathway was activated by nano-Se biofortification, which increased apigenin and caffeic acid concentrations. The high-level expression of the related genes (TaBx1A, TaBx3A, TaBx4A, TaASMT2, and TaCOMT) induced the promotion of melatonin (88.6%) and 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one (DIMBOA) (64.3%). Different ratios of the secondary metabolites to nano-Se were taken to examine the effects on resistance of wheat to S. avenae. The results revealed that the combination of nano-Se and melatonin could achieve the best overall performance by reducing the S. avenae number by 52.2%. The study suggests that the coordinated applications of nano-Se and melatonin could more effectively improve the wheat resistance to aphids via the promotion of volatile organic compound synthesis and modulation in phenylpropane and indole metabolism pathways.

Selenium improved the combined remediation efficiency of Pseudomonas aeruginosa and ryegrass on cadmium-nonylphenol co-contaminated soil

Most chemical plant wastewater contains both organic and inorganic pollutants, which are easy to diffuse along with surface runoff. The combined pollution of nonylphenol (NP) and cadmium (Cd) in soil is a serious problem that has not attracted enough attention. Based on the effects of selenium (Se) and Pseudomonas aeruginosa (P. aeruginosa) on plant and soil microbial communities, we speculated that the application of Se and P. aeruginosa in soil could improve the phytoremediation efficiency of ryegrass on contaminated soil. In this study, pot experiments with Cd and NP co-contaminated soil were conducted, and the results showed that application of P. aeruinosa alone could improve the removal rates of NP and Cd by ryegrass, and the supplementary of Se further enhanced the effect of micro-phyto remediation, with the highest removal rates of NP and Cd were 79.6% and 49.4%, respectively. The application of P. aeruginosa plus Se reduced the adsorption of Cd and NP through C-O and Si-O-Fe of the soil, changed the enzyme activity, and also affected the changing trend of the microbial community in soil. Pseudomonas, Sphingomonadales, Nitrospira, and other beneficial bacteria were enriched after a 60-day period with P. aeruginosa and Se treatment, thus promoting the removal of NP and Cd. In light of the above results, we suggest that P. aeruginosa application can efficiently facilitate the phytoremediation of ryegrass on Cd-NP co-contaminated soil, and Se supplementation in soil showed the synergistic effect on the remediation.

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.

Melatonin elevated Sclerotinia sclerotiorum resistance via modulation of ATP and glucosinolate biosynthesis in Brassica rapa ssp. pekinensis

Sclerotinia stem rot is a common disease found in Brassica rapa that is caused by the necrotic plant pathogen Sclerotinia sclerotiorum. Melatonin (MT) has known biological activity and effectively relieved this type of Sclerotinia stem rot in B. rapa. To better understand the mechanisms behind MT-induced S. sclerotiorum resistance in B. rapa, we performed both proteomic and metabolomic analysis. Our results showed that during S. sclerotiorum infection, thiamine synthesis was activated and defended against it. In infected leaves, ribosomal synthesis-related proteins responded positively to MT treatment. Integrated proteomic and metabolomic analysis showed that amino acid metabolism was activated by MT treatment. After MT treatment, adenosine-triphosphate (ATP) content and the activity of antioxidant enzymes were both increased in B. rapa infected leaves. Cysteine synthase, sulfur transfer-related proteins, and glucosinolate (GS) were all increased after MT treatment in infected B. rapa leaves. Taken together, these results indicated that B. rapa leaves promoted thiamine formation to defend against S. sclerotiorum infection. Moreover, MT helped further induce antioxidant activation in B. rapa in an ATP-dependent manner and stimulating GS biosynthesis to well inhibit the S. sclerotiorum infection. SIGNIFICANCE: Melatonin (MT) has biological activity and effectively relieved the Sclerotinia stem rot of Brassica rapa caused by the necrotic plant pathogen Sclerotinia sclerotiorum. In order to reveal the molecular mechanisms of MT-induced S. sclerotiorum resistance in B. rapa, comprehensive proteomic and metabolomic analyses were conducted. The integration analysis of omic-data illustrated that the modulation of ATP and glucosinolate biosynthesis induced by MT administration helped to defend the infection of S. sclerotiorum in B. rapa. Our results will provide insights into MT-induced anti-fungal mechanism and therapeutic strategies to mitigate Sclerotinia stem rot of B. rapa, thereby increasing plant yield and decreasing economic losses.

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.

Transcriptomic Characterization of the Effects of Selenium on Maize Seedling Growth

Selenium (Se) is a trace mineral element in soils that can be beneficial to plants in small amounts. Although maize is among the most economically important crops, there are few reports on the effects of Se on maize seedling growth at the molecular level. In this study, the growth of maize seedlings treated with different concentrations of Na₂SeO₃ was investigated, and the physiological characteristics were measured. Compared with the control, a low Se concentration promoted seedling growth, whereas a high Se concentration inhibited it. To illustrate the transcriptional effects of Se on maize seedling growth, samples from control plants and those treated with low or high concentrations of Se were subjected to RNA sequencing. The differentially expressed gene (DEG) analysis revealed that there were 239 upregulated and 106 downregulated genes in the low Se treatment groups, while there were 845 upregulated and 1,686 downregulated DEGs in the high Se treatment groups. Both the Gene Ontology (GO) and the Kyoto Encyclopedia of Genes and Genomes (KEGG) annotation analyses showed a low concentration of the Se-stimulated expression of "DNA replication" and "glutathione (GSH) metabolism"-related genes. A high concentration of Se repressed the expression of auxin signal transduction and lignin biosynthesis-related genes. The real-time quantitative reverse transcription PCR (qRT-PCR) results showed that in the low Se treatment, "auxin signal transduction," "DNA replication," and lignin biosynthesis-related genes were upregulated 1.4- to 57.68-fold compared to the control, while, in the high Se concentration treatment, auxin signal transduction and lignin biosynthesis-related genes were downregulated 1.6- to 16.23-fold compared to the control. Based on these transcriptional differences and qRT-PCR validation, it was found that a low dosage of Se may promote maize seedling growth but becomes inhibitory to growth at higher concentrations. This study lays a foundation for the mechanisms underlying the effects of Se on maize seedling growth.

Enhancement and improvement of selenium in soil to the resistance of rape stem against Sclerotinia sclerotiorum and the inhibition of dissolved organic matter derived from rape straw on mycelium

Sclerotinia stem rot (SSR), caused by Sclerotinia sclerotiorum (S. sclerotiorum), one of the most destructive diseases in many crops including Brassica napus L. The extensive use of fungicides to control S. sclerotiorum caused severe damage to the environment in the long term. Increasing study reported that selenium (Se) is a beneficial element for plant by promoting growth and enhancing disease resistance. In this study, it was found that Se in soil shortened lesion length by 19.14% on rape stem infected with S. sclerotiorum. While resistance mechanism of rape stem against S. sclerotiorum remains unknown. Transcriptomic analysis of rape stem was performed and the results indicated that genes related to antifungal pathways were up-regulated. Moreover, metabonomic analysis was carried out to study the inhibitive effect of the dissolved organic matter derived from rape straw with Se pretreatment in soil (RSDOM_Se) on S. sclerotiorum mycelium, results showed that RSDOM_Se caused severe damage to energy metabolism of mycelium. Further study indicated that RSDOM_Se decreased the pathogenicity of mycelium on rape leaves significantly, and enhanced content of chlorophyII, carotenoids, OD phenol and activities of phenylalanine ammonia-lyase (PAL), polyphenol oxidase (PPO) in rape leaves, which suggested that RSDOM_Se plays a positive role in regulating oxidative stress responses of plant when infected with S. sclerotiorum. In addition, when compared with dimcthachlon (DIM) treatment alone, DIM combined with RSDOM_Se resulted in higher inhibition on mycelial growth of S. sclerotiorum (the inhibition ratio of nearly 60%). Results in this study suggested that Se enhanced the resistance of rape stem against S. sclerotiorum because of the up-regulated genes related to antifungal pathways, and RSDOM_Se improved the mycelial growth inhibition and decreased the pathogenicity of mycelium on rape leaves. Overall, Se as well as Se-enrich byproducts, possessed great potential to be developed as ecological fungicides for controlling S. sclerotiorum.

The Effects of Selenium on Wheat Fusarium Head Blight and DON Accumulation Were Selenium Compound-Dependent

Fusarium head blight (FHB) caused by Fusarium graminearum not only results in severe yield losses, but also contaminates wheat grains with deoxynivalenol (DON) toxins. Prevention and control of FHB and DON contamination rely mainly on resistant varieties and fungicides. Selenium (Se) is an essential element for humans and animals, and also a beneficial element for plants. In this work, four Se compounds, i.e., sodium selenite (Na₂SeO₃), sodium selenate (Na₂SeO₄), selenomethionine (SeMet) and selenocysteine (SeCys₂), were supplemented in a trichothecene biosynthesis induction (TBI) solid medium at different dosages in in vitro experiments. The four Se compounds at the dosage of 20 mg∙L⁻¹ were sprayed onto wheat spikes immediately after inoculation at anthesis. All four of the Se compounds significantly inhibited the mycelial growth and DON production in the in vitro experiment; however, in planta, their effects on FHB severity and toxin accumulation in grains were compound-dependent. SeMet consistently negatively regulated fungal growth and DON accumulation both in vitro and in planta, which could be a novel and proconsumer strategy for reducing the detriment of wheat FHB disease and DON accumulation.

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.