High potential for selenium biofortification of lentils ( Lens culinaris L.)

Beneficial forms of selenium (Se) and their impact on human health are a global topic of interest in public health. We are studying the genetic potential for Se biofortification of pulse crops to improve human nutrition. Lentils ( Lens culinaris L.) are an important protein and carbohydrate food and are a valuable source of essential dietary components and trace elements. We analyzed the total Se concentration of 19 lentil genotypes grown at eight locations for two years in Saskatchewan, Canada. We observed significant genotypic and environmental variation in total Se concentration in lentils and that total Se concentration in lentils ranged between 425 and 673 microg kg(-1), providing 77-122% of the recommended daily intake in 100 g of dry lentils. Over 70% of the Se was present as selenomethionine (SeMet) with a smaller fraction (<20%) as inorganic Se and very small amounts as selenocysteine (SeCys). We found that soils from the locations where the lentils were grown were rich in Se (37-301 microg kg(-1)) and that lentils grown in Saskatchewan have the potential to provide an excellent natural source of this essential element. Our analyses gave us a preliminary understanding of the genetic basis of Se uptake in lentil and indicated that any potential strategy for micronutrient biofortification in lentil will require choice of field locations that minimize the spatial variability of soil Se content.     

Assessment of Arsenic and Selenium Concentration with Chlorophyll Contents of Sugar Beet (Beta vulgaris var.saccharifera) and Wheat (Triticum aestivum) Exposed to Municipal Sewage Sludge Doses

The present study was conducted to assess the suitability of sewage sludge amendment in soil for Beta vulgaris var. saccharifera (sugar beet) and Triticum aestivum (wheat) by evaluating the arsenic and selenium accumulation and physiological responses of plants grown at 10%, 25%, and 50% sewage sludge amendment rate. Sewage sludge amendment was modified by the physicochemical properties of soil, thus increasing the availability of heavy metals in the soil and consequently with higher accumulation in plant parts. The chlorophyll contents increased after the sewage sludge treatments except for 50%. The sewage sludge amendment led to a significant increase in arsenic and selenium concentrations of the soil. The heavy metal accumulation in the soil after the treatments did not exceed the limits for the land application of sewage sludge recommended by the US Environmental Protection Agency. The increased concentration of heavy metals in the soil due to the sewage sludge amendment led to increases in heavy metal uptake in the leaves and root concentrations of arsenic and selenium in plants as compared to those grown on unamended soil. Accumulation was more in roots than shoots and leaves for most of the heavy metals. Concentrations of arsenic and selenium were more than the permissible limits of national standards in the edible portion of sugar beet and wheat grown on different sewage sludge amendments ratios. The study concludes that the sewage sludge amendment in the soil for growing sugar beet and wheat may not be a good option due to risk of contamination of arsenic and selenium.     

Determination of arsenic and selenium in whole fish by continuous-flow hydride generation atomic absorption spectrophotometry

A combined wet chemical and dry ash digestion and use of a continuous-flow hydride generator coupled with a flame-heated quartz cell enabled the simple, precise, and highly automated atomic absorption determination of arsenic and selenium in tissues of whole fish. Percent relative standard deviation averaged 4% for each element; method detection limits (micrograms/g dry wt) were about 0.06 for arsenic and 0.04 for selenium. Digestion of samples proceeded with little operator attention and without perchloric acid. Analysis for arsenic as As(V) simplified sample preparation but care had to be exercised to avoid interferences from high concentrations of selenium.     

Tumorigenesis, metabolism, speciation, bioavailability, and tissue deposition of selenium in selenium-enriched ramps (Allium tricoccum)

Ramps (Allium tricoccum) were grown either in a mixture of vermiculite and peat moss or hydroponically with various concentrations of selenium as sodium selenate. The concentrations used were from 30 to 300 mg of selenium/kg of vermiculite-peat moss or from 10 to 120 mg/L in the hydroponic solutions. Levels as high as 784 mg of selenium/kg were obtained in the ramp bulbs when grown with high levels of selenium in the vermiculite-peat moss, and up to 600 mg of selenium/kg was obtained hydroponically. The predominant form of selenium in the ramp bulbs at all concentrations of selenium was Se-methylselenocysteine, with lower amounts of selenate, Se-cystathionine, and glutamyl-Se-methylselenocysteine. There was a approximately 43% reduction in chemically induced mammary tumors when rats were fed a diet with Se-enriched ramps. Dietary Se-enriched ramps for rats did not result in excessive tissue selenium accumulation or undesirable side effects. Bioavailability studies with rats indicated that selenium in ramps was 15-28% more available for regeneration of glutathione peroxidase activity than inorganic selenium as selenite. Therefore, Se-enriched ramps appear to have potential for the reduction of cancer in humans.     

Vegetables collected in the cultivated Andean area of northern Chile: total and inorganic arsenic contents in raw vegetables.

High levels of arsenic are found in the soil and water of the Second Region in Chile as a result of natural causes. Total and inorganic arsenic contents were analyzed in the edible part of 16 agricultural products (roots, stems, leaves, inflorescences, and fruits) grown in this area. The total arsenic contents varied in the range 0.008-0.604 microg g(-1) of wet weight (ww), below the maximum level allowed by Chilean legislation (1 microg(-1) of ww). Inorganic arsenic contents (range = 0.008-0.613 microg(-1) of ww) represented between 28 and 114% of total arsenic. The concentrations of total and inorganic arsenic found in edible roots and leaves were higher than those found in fruit. The highest concentrations were found in a sample of spinach. High quantities of this vegetable would have to be consumed (250 g/day) to reach the Provisional Tolerable Weekly Intake for inorganic arsenic. The vegetable group may make a considerable contribution to the total intake of inorganic arsenic.     

Status and behavior of natural and technogenic forms of As, Sb, Se, and Te in ore tailings and contaminated soils: A review

The variable oxidative status that is common for arsenic, antimony, selenium, and tellurium makes them specifically sensitive to the redox conditions in soils. All these elements are siderophiles, being well adsorbed by iron hydroxides. At the same time, metalloids also show individual behavior in soils. The most common valence for arsenic is III and V. Arsenic III is more mobile and more toxic than arsenic V. Unlike arsenic, antimony, selenium, and tellurium appear to be more mobile at a higher oxidation degree. Two main oxidation degrees (III and V) are typical of antimony in soils, whereas four oxidation degrees (-II, 0, IV, and VI) are typical of selenium and tellurium.     

Environmental Arsenic and Selenium Contamination and Approaches Towards Its Bioremediation Through the Exploration of Microbial Adaptations: A Review

Bioaccumulation of selenium and arsenic resulting from geogenic activities and aggravated by anthropogenic actions has now become a serious environmental issue. Different parts of the world are experiencing issues of selenium and arsenic contamination, especially in soil and groundwater. The present selenium and arsenic contamination scenario has been well represented in contemporary literature, and there are an array of remediation techniques targeting the decontamination of environmental contamination. The use of microbe-mediated remediation of selenium and arsenic contamination is gaining scientific attention for sustainable environmental bioremediation. The present review elucidates the different aspects of selenium and arsenic contamination, bioaccumulation, and bioremediation with implications for successful decontamination of these heavy metals.     

叶面喷施硅和硒对水稻砷积累及光合参数的影响

本文采用盆栽试验，研究了在砷污染土壤上，水稻叶面分别喷施硅溶液、硒溶液和硅硒混合溶液对籽粒砷含量相对较低的水稻品种旌1优华珍和C两优华占以及籽粒砷含量相对较高的水稻品种丰优香占砷积累和光合参数的影响。试验结果表明，3种叶面喷施处理相比较而言，以叶面单独喷施硅降低水稻籽粒砷含量效果最好，优于叶面单施硒和叶面喷施硅硒混合液处理。叶面单独喷施硅与对照相比，显著降低了籽粒砷含量相对较低的两个水稻品种的籽粒砷含量，但对籽粒砷含量相对较高的水稻品种则没有显著影响。籽粒砷含量相对较低的水稻品种更多比例的砷固定在茎中使其稻米砷积累量较低。3种叶面喷施处理与对照相比均提高了水稻光合参数(如光合速率、气孔导度、胞间CO₂浓度)，光合参数与水稻砷浓度呈负相关关系，叶面喷施硅或硒对水稻叶片光合参数的影响差异可能是造成籽粒砷含量差异的重要原因，不同水稻品种叶片光合参数对外源硅或硒的敏感度或响应度不同。总之，叶面喷施硅溶液对改善水稻光合参数的效果最好，是减少水稻籽粒砷含量一项经济有效的措施，在生产应用实践中，要注意作物品种间的差异。     

Bioaccumulation potential of dietary arsenic, cadmium, lead, mercury, and selenium in organs and tissues of rainbow trout (Oncorhyncus mykiss) as a function of fish growth

The distribution and potential bioaccumulation of dietary arsenic, cadmium, lead, mercury, and selenium in organs and tissues of rainbow trout (Oncorhyncus mykiss Walbaum, 1792), a major aquaculture species, was studied in relation to fish growth over a period of >3 years. Fish were reared under normal farming conditions, that is, fed a standard fish food and exposed to negligible levels of waterborne trace elements. The age-related variations in the content of each trace element in gills, kidney, liver, muscle, and skin were studied through nonparametric regression analysis. A buildup of all elements in all tissues and organs was observed, but due to dilution with growth, the concentrations did not increase, except in a few cases such as cadmium and mercury in liver and kidney. In muscle tissue, the concentrations of mercury, lead, and selenium did not alter significantly with growth, whereas cadmium increased but remained at exceedingly low levels. The concentration of arsenic in muscle tissue peaked at 14 months and then decreased in adult specimens. Arsenic speciation by high-performance liquid chromatography--inductively coupled plasma mass spectrometry revealed that arsenic in muscle was almost exclusively present in the form of nontoxic arsenobetaine. Application of a mercury mass balance model gave predicted concentrations in agreement with measured ones and showed that in farmed rainbow trout the ratio of mercury concentrations in feed and in fish is about 1:1. Therefore, rainbow trout does not approach the limits established for human consumption even when reared with feed at the maximum permitted levels. These findings highlight the low bioaccumulation potential of toxic trace elements such as cadmium, lead, and mercury in rainbow trout following dietary exposure. On the other hand, selenium concentrations in muscle (about 0.2 microg g (-1) of fresh weight) show that rainbow trout may be a good source of this essential element.     

Cultivar effects on nitrogen fixation in peas and lentils

Increasing nitrogen fixation in legume crops could increase cropping productivity and reduce nitrogen fertilizer use. Studies have found that crop genotype, rhizobial strain, and occasionally genotype-specific interactions affect N fixation, but this knowledge has not yet been used to evaluate or breed for greater N fixation in US crops. In this study five USDA varieties of lentils (Lens culinaris Medik.) and five varieties of peas (Pisum sativum L.) were tested with 13 to 15 commercially available strains of Rhizobium leguminoserum bv. viciae to identify the better N fixing rhizobial strains, crop varieties, and specific pairings. Peas and lentils inoculated with individual strains were grown in growth chambers for 6 week. Plants received (¹⁵NH₄)₂ SO₄ (5 at.%) starter fertilizer to measure N fixation by isotope dilution. Below- and above-ground biomass, numbers of nodules, and the proportion of plant N supplied by fixation (PNF) were determined. The percent of N fixed was significantly affected by crop variety and significantly correlated with number of nodules in both lentils and peas. This implies that one strategy for enhancing crop N fixation is developing varieties that have higher rhizobium infection rates. Total N fixation in lentils was significantly influenced by both crop variety and rhizobial strain. Eston variety lentil and Shawnee variety pea had the highest PNF of 80.8% and 91.3%, respectively. The different strains of R. leguminoserum affected PNF in lentils but not in peas. These findings suggest that N fixation improvement in lentils and peas may be addressed most effectively by breeding crops for greater N fixation hosting capacity.     

Composition,Nutritional Value,and Health Benefits of Pulses

The United Nations has declared 2016 as the International Year of Pulses. Pulses are narrowly defined as leguminous crops that are harvested as dry seeds. Although some pulse crops are harvested green (e.g., green peas), these are classified as vegetables because the pods are often consumed along with the mature and sometimes immature seeds. Other dried legumes such as soybean and peanut meet the definition of being a leguminous crop that is harvested as dry seeds; however, these crops are grown primarily for oil content and, thus, are not categorized as pulses. There are hundreds of pulse varieties grown worldwide; these include, for example, dry edible beans, chickpeas, cowpeas, and lentils. This review will cover the proximate (e.g., protein, carbohydrates, vitamins, and minerals), and phytonutrient (e.g., polyphenolics and carotenoid) composition of dry edible beans, peas, lentils, and chickpeas. Soybean and peanuts will not be covered in this review. The effects of processing on composition will also be covered. The health benefits related to folates, fiber, and polyphenolics will be highlighted. The health benefits discussed will include cardiovascular disease, cancer, diabetes, and weight control. The current review will not cover antinutrient compounds; this topic will be covered in a separate review article published in the same issue.     

Selenium species bioaccessibility in enriched radish (Raphanus sativus): a potential dietary source of selenium

An in vitro gastrointestinal method was employed to predict the potential bioavailability of selenium and its species from radish, belonging to the Brassicaceae family, grown in hydroponics media in the presence of inorganic selenium, such as Na2SeO3 and Na2SeO4. A low transformation of Se into organic forms was observed in radish plants grown in Se(VI)-enriched culture media. On the contrary, in those plants exposed to selenite, >95% of the total selenium was found as selenocystine (SeCys2), selenomethionine (SeMet), and Se-methylselenocysteine (SeMetSeCys). The concentrations of these species in fresh samples remained almost unaltered after a simulated gastrointestinal digestion. Therefore, a high selenium content of Se-methylselenocysteine (65%), previously reported as a cancer chemopreventive species, remained in the potentially bioabsorbable fraction. As these plants usually undergo a short development cycle, these results suggest that radish enriched in selenite could be a good choice as an organoselenium supplement for the human diet and animal feed.     

Some Canadian-grown potato cultivars contribute to a substantial content of essential dietary minerals

Potato consumption provides significant dietary contributions to several essential minerals, but the effects of cultivar and planting site are not well-understood. The mineral content of 16 cultivars, grown at 5 locations, was measured using inductively coupled plasma-optical emission spectroscopy and evaluated on a per serving basis for percent recommended daily intake (% RDI), emphasizing some minerals where global deficiencies are common (calcium, iron, selenium, and zinc). Discriminant analysis showed that both genotype and growing location were important. Differences in mineral content occurred between cultivars at each site, specific cultivars at different sites, and collectively between sites. 'Freedom', 'Yukon Gold', and particularly the very stable mineral source 'Russet Burbank' contributed most to the % RDI for minerals. One serving per day of these cultivars provides a significant contribution to the % RDI for the macrominerals magnesium, phosphorus, and potassium and the trace minerals copper, iron, selenium, and zinc.     

Survey of total and inorganic arsenic content in blue mussels (Mytilus edulis L.) from Norwegian fiords: revelation of unusual high levels of inorganic arsenic

The present study reports the findings of unusual high levels of inorganic arsenic in samples of blue mussels (Mytilus edulis L.). A total of 175 pooled samples of blue mussels from various locations along the Norwegian coastline were analyzed for their content of total arsenic and inorganic arsenic. Total arsenic was determined using inductively coupled plasma mass spectrometry (ICPMS) following microwave-assisted acidic digestion of the samples. Inorganic arsenic was determined using an anion-exchange HPLC-ICPMS method following microwave-assisted alkaline solubilization of the samples. For the majority of the samples (78%) the concentration of total arsenic was below 3 mg kg(-1) wet weight (ww) and inorganic arsenic constituted <9% of the total arsenic (i.e., <0.25 mg kg(-1) ww). However, in some samples higher concentrations of total arsenic were found (up to 13.8 mg kg(-1) ww) and the inorganic arsenic content constituted up to 42% of the total arsenic (up to 5.8 mg kg(-1) ww). These are among the highest inorganic arsenic concentrations reported so far for marine animals. The findings of samples with concentrations of inorganic arsenic above 0.53 mg kg(-1) ww were restricted to sampling sites from two counties, Sogn and Fjordane and Hordaland, whereas samples from the rest of the country showed lower inorganic arsenic concentrations. Consumption of a meal containing 200 g of the blue mussels with the highest content of inorganic arsenic would for a 70 kg person lead to a 10% excess of the provisional tolerable weekly intake (PTWI) value for inorganic arsenic of 15 microg kg(-1) of body weight week(-1).     

Enriched accumulation and biotransformation of selenium in the edible seaweed Laminaria japonica

Accumulations of selenium in kelp Laminaria japonica cultured in seawater was achieved by adding selenite (Na2SeO3) with or without N-P (NaNO3 + NaH2PO4) nutrients at different concentrations. Biotransformation of selenium in the kelp was investigated through measuring the selenium of biological samples and different biochemical fractionations. The results showed that the optimal selenite-enrichment concentration is 200 mg L(-1), which can allow the kelp to accumulate a total selenium content from 0.51 +/- 0.15 to 26.23 +/- 3.12 microg g(-1) of fresh weight (fw). Selenium composition analysis of kelp (control group) showed that selenium is present as organic selenium, which is up to 86.22% of the total selenium, whereas inorganic selenium is barely 4.85%. When L. japonica was exposed for 56 h in seawater containing 200 mg L(-1) Na2SeO3, the organic selenium was 16.70 microg g(-1) of fw (68.23%) and inorganic selenium was 4.71 microg g(-1) of fw (19.26%). The capability of accumulation of selenium was further enhanced by adding N-P nutrients to the selenite-enriched medium. Total selenium is increased to be 33.65 microg g(-1) of fw at optimal concentration of N-P nutrient (150 mg L(-1) NaNO3 and 25 mg L(-1) NaH2PO4), whereas the inorganic selenium was not increased and remained at 4.597 microg g(-1) of fw (13.36%), and the increased part of selenium was organic selenium. This implied that kelp L. japonica could effectively transform inorganic selenium into organic selenium through metabolism.     

水稻不同品种在海南富硒土壤中硒的吸收和分配机理

利用盆栽研究了5个水稻品种在两种不同的富硒土壤中Se吸收累积的生育期动态变化和Se在水稻植株不同部位的分配机理.结果表明,随着生长发育期的推进,水稻在孕穗期对Se含量和累积量同时骤增,从苗期到孕穗期水稻Se的累积量占总Se累积量的45.5%～67%,同时Se含量也达到最高,说明这一段时期是水稻吸收Se的关键时期;在富硒土壤1中水稻各器官Se含量都显著大于相应土壤2中水稻各器官,水稻各器官Se含量顺序依次为根>叶>茎>籽粒,Se易向营养体富集;5个水稻品种中只有杂交稻在土壤1中生长正常;3个常规水稻中旱14、2004-95、稻翅品种在土壤2中的SOD、POD酶活性比土壤1中呈明显减小趋势,但杂交稻特优10 SOD酶活性变化相反,其POD酶活性变化的幅度也最小;在土壤2中5个水稻品种生长都正常,杂交稻的平均硒含量最低,但累积量最高.     

Assessment of Arsenic Toxicity and Tolerance Characteristics of Bean Plants (Phaseolus Vulgaris) Exposed to Different Species of Arsenic

Experiments were conducted to evaluate the arsenic toxicity, its accumulation and phytoremediation potential of bean plants (Phaseolus vulgaris) grown in soils contaminated with different species of arsenic such as arsenite (As(III)), arsenate (As(V)) and dimethylarsinic acid (DMA). Bean plants were grown in soils amended by aqueous solutions of 20 and 50 mg kg^?1 of As (III), As(V) or DMA. Arsenic species negatively affected the yield and growth of the plant. The study demonstrated arsenic accumulation in the plant parts. The concentration of arsenic compounds in the shoots decreased in the order arsenate > arsenite > dimethylarsinic acid while in the roots as arsenite > arsenate > dimethylarsinic acid. Most arsenic is accumulated in the roots with limited transfer to shoots. Thus, bean plants can be considered as an arsenic excluder and has the potential for phytostabilization of arsenic contaminated sites. The study also reveals that removal of arsenic by boiling the vegetables with excess of water is not possible.     

Selenium speciation in soil and rice: influence of water management and Se fertilization

Rice (Oryza sativa) is the staple food for half of the world's population, but the selenium (Se) concentrations in rice grain are low in many rice-growing regions. This study investigated the effects of water management on the Se speciation dynamics in the soil solution and Se uptake and speciation in rice in a pot experiment. A control containing no Se or 0.5 mg kg(-1) of soil of selenite or selenate was added to the soil, and plants were grown under aerobic or flooded conditions. Flooding soil increased soluble Se concentration when no Se or selenite was added to the soil, but decreased it markedly when selenate was added. Selenate was the main species in the +selenate treatment, whereas selenite and selenomethionine selenium oxide were detected in the flooded soil solutions of the control and +selenite treatments. Grain Se concentration was 49% higher in the flooded than in the aerobic treatments without Se addition. In contrast, when selenate or selenite was added, the aerobically grown rice contained 25- and 2-fold, respectively, more Se in grain than the anaerobically grown rice. Analysis of Se in rice grain using enzymatic hydrolysis followed by HPLC-ICP-MS and in situ X-ray absorption near-edge structure (XANES) showed selenomethionine to be the predominant Se species. The study showed that selenate addition to aerobic soil was the most effective way to increase Se concentration in rice grain.     

Establishment of selenium uptake and species distribution in lupine, Indian mustard, and sunflower plants

Selenium has been recognized as essential for all mammals; therefore, its concentration level and speciation are of great concern. Plants are one of the main sources of selenium in the diet. Thus, inorganic selenium uptake and its transformation in different species were evaluated in Indian mustard (Brassica juncea), sunflower (Helianthus annus), and white lupine (Lupinus albus). More than 1.2 g x kg(-)(1) (dry matter) of Se was found in the aerial part of Indian mustard when growing on 1 mg x L(-)(1) of Se as Na(2)SeO(4), and approximately half this amount was determined in the leaves of the lupine, which is still quite high. Selenomethionine was the main selenium-containing amino acid identified in most of the extracts by HPLC-ICP-MS. The higher values were 6.8 and 14.5 mg x kg(-)(1) (expressed as Se in dry matter) in the leaves of lupine and sunflower, respectively. This is of great importance because some authors have considered the combination of this enriched material with non-enriched food as a source of selenium supplementation.     

Proanthocyanidin composition in the seed coat of lentils (Lens culinaris L.)

Lentils (Lens culinaris L.) are a popular food in many countries. However, little is known about their phenolic composition. Because polyphenols in lentils are located essentially in their seed coat, the objective of this work was to study the composition of proanthocyanidins, the major group of polyphenols, in this part of the tissue. The use of C(18) Sep-Pak cartridges permitted the fractionation of lentil seed coat extract into monomer, oligomer, and polymer proanthocyanidin fractions. Subsequent thiolysis of oligomer and polymer fractions followed by HPLC analysis allowed the mean degree of polymerization (mDP) and the structural composition of proanthocyanidins to be determined. A fractionation of lentil seed coat extracts on a polyamide column followed by HPLC and HPLC-DAD-MS analyses was used to identify the individual proanthocyanidins. The results showed that the major monomeric flavan-3-ol was (+) catechin-3-glucose, with lesser amounts of (+)-catechin and (-)-epicatechin. In the oligomer fraction, various dimer, trimer, and tetramer proanthocyanidins constituted of catechin, gallocatechin, and catechin gallate units were identified, and several procyanidins and prodelphinidins from pentamers to nonamers constitute the polymer fraction. The most abundant proanthocyanidins in the seed coat of lentils are the polymers (65-75%), with a mDP of 7-9, followed by the oligomers (20-30%), with a mDP of 4-5.