Search

Iodine deficiency disorders (IDD) in sub-Saharan African countries are related to low dietary I intake and generally combatted through salt iodisation. Agronomic biofortification of food crops may be an alternative approach. This study assessed the effectiveness of I biofortification of green vegetables (Brassica napus L and Amaranthus retroflexus L.) grown in tropical soils with contrasting chemistry and fertility. Application rates of 0, 5 and 10 kg ha−1I applied to foliage or soil were assessed. Leaves were harvested fortnightly for ~ 2 months after I application before a second crop was grown to assess the availability of residual soil I. A separate experiment was used to investigate storage of I within the plants. Iodine concentration and uptake in sequential harvests showed a sharp drop within 28 days of I application in all soil types for all I application levels and methods. This rapid decline likely reflects I fixation in the soil. Iodine biofortification increased I uptake and concentration in the vegetables to a level useful for increasing dietary I intake and could be a feasible way to reduce IDD in tropical regions. However, biofortification of green vegetables which are subject to multiple harvests requires repeated I applications.

Aim Magnesium (Mg) deficiency (known as grass tetany) is a serious metabolic disorder that affects grazing ruminants. We tested whether Mg-fertiliser can increase Mg concentration of Italian ryegrasses (Lolium multiflorum L.) including a cultivar (cv. Bb2067; ‘Magnet’), bred to accumulate larger concentrations of Mg. Methods Under controlled environment (CE) conditions, three cultivars (cv. Bb2067, cv. Bb2068, cv. RvP) were grown in low-nutrient compost at six fertiliser rates (0–1500 μM MgCl2.6H2O). Under field conditions, the three cultivars in the CE condition and cv. Alamo were grown at two sites, and four rates of MgSO4 fertiliser application rates (0–200 kg ha−1 MgO). Multiple grass cuts were taken over two-years. Results Grass Mg concentration increased with increasing Mg-fertiliser application rates in all cultivars and conditions. Under field conditions, cv. Bb2067 had 11–73% greater grass Mg concentration and smaller forage tetany index (FTI) than other cultivars across the Mg-fertiliser application rates, sites and cuts. Grass dry matter (DM) yield of cv. Bb2067 was significantly (p p ≥ 0.05). Conclusions Biofortification of grass with Mg through breeding and agronomy can improve the forage Mg concentration for grazing ruminants, even in high-growth spring grass conditions when hypomagnesaemia is most prevalent. Response to agronomic biofortification varied with cultivar, Mg-fertiliser rate, site and weather. The cost:benefit of these approaches and farmer acceptability, and the impact on cattle and sheep grazing on grasses biofortified with Mg requires further investigation.

Iodine is an essential trace element for humans and grazing animals and is often deficient. Our aim was to investigate the role of soil properties in retaining and ‘fixing' iodine in soils and thereby controlling its phyto-availability to grass. Soils were spiked with labelled 129IO3− and rye grass (Lolium perenne L.) was grown to measure iodine uptake by grass as a function of yield, soil properties and continuous 127I inputs from irrigation water. Iodine-129 added at the start of the uptake trial was rapidly fixed (t1/2 c. 40 h) into non-labile humus-bound forms in soil. The 129I/127I isotopic ratio in grass, compared to the ratio in soil, declined over time confirming progressive 129I fixation into the soil solid phase. The rate of fixation was controlled by soil properties. A model describing iodine dynamics and uptake accounted for c. 75% of the variation in iodine concentration in grass. For most of the soils studied, the main source of iodine in herbage probably arises from the transient availability of periodic rainfall inputs rather than from soil sources. This is expected to improve biofortification strategies.

Correlations between juvenile wheat root traits, and grain yield and yield component traits under optimal field conditions have previously been reported in some conditions. The aim of this study was to test the hypothesis that juvenile wheat root traits correlate with yield, yield components and grain mineral composition traits under a range of soil environments in India. A diverse panel of 36 Indian wheat genotypes were grown for ten days in ‘pouch and wick’ high-throughput phenotyping (HTP) system (20 replicates). Correlations between juvenile root architecture traits, including primary and lateral root length, and grain yield, yield components and grain mineral composition traits were determined, using field data from previously published experiments at six sites in India. Only a limited number of juvenile root traits correlated with grain yield (GYD), yield components, and grain mineral composition traits. A narrow root angle, potentially representing a ‘steep’ phenotype, was associated with increased GYD and harvest index (HI) averaged across sites and years. Length related root traits were not correlated with GYD or HI at most sites, however, the total length of lateral roots and lateral root number correlated with GYD at a sodic site of pH 9.5. The total length of lateral roots (TLLR) correlated with grain zinc (Zn) concentration at one site. A wider root angle, representing a shallow root system, correlated with grain iron (Fe) concentration at most sites. The total length of all roots (TLAR) and total length of primary roots (TLPR) correlated with grain S concentration at most sites. Narrow root angle in juvenile plants could be a useful proxy trait for screening germplasm for improved grain yield. Lateral root and shallow root traits could potentially be used to improve grain mineral concentrations. The use of juvenile root traits should be explored further in wheat breeding for diverse environments.

Selenium (Se) biofortification of staple cereal crops can improve the Se nutritional status of populations. A field trial employing an enriched stable isotope of Se (77Se) was undertaken over three consecutive cropping seasons in a coarse-textured, calcareous soil in Gilgit-Baltistan, Pakistan. The objectives were to (1) assess the feasibility and efficiency of Se biofortification, (2) determine the fate of residual Se, and (3) assess the consequences for dietary Se intake. Isotopically enriched 77Se (77SeFert) was applied, either as selenate or as selenite, at three levels (0, 10, and 20 g ha−1) to a wheat crop. Residual 77SeFert availability was assessed in subsequent crops of maize and wheat without further 77SeFert addition. Loss of 77SeFert was c.35% by the first (wheat) harvest, for both selenium species, attributable to the practice of flood irrigation and low adsorption capacity of the soil. No 77SeFert was detectable in subsequent maize or wheat crops. The remaining 77SeFert in soil was almost entirely organically bound and diminished with time following a reversible (pseudo-)first-order trend. Thus, repeat applications of Se would be required to adequately biofortify grain each year. In contrast to native soil Se, there was no transfer of 77SeFert to a recalcitrant form. Grain from control plots would provide only 0.5 µg person−1 day−1 of Se. By contrast, a single application of 20 g ha−1 SeVI could provide c. 47 µg person−1 day−1 Se in wheat, sufficient to avoid deficiency when combined with dietary Se intake from other sources (c. 25 µg day−1).

Zinc (Zn) is an essential nutrient for human health. In Ethiopia, a high prevalence of Zn deficiency has been reported. To explore demographic variation and spatial dependencies in the Zn status of the Ethiopian population, we analyzed archived serum samples (n = 3373) from the 2015 Ethiopian National Micronutrient Survey (ENMS), a cross-sectional survey of young children, school-age children, women of reproductive age (WRA) and men conducted in all 9 regions and two city administration of Ethiopia. Serum Zn concentrations, measured using inductively coupled plasma-mass spectrometry (ICPMS), were compared to thresholds based on age, sex, fasting status, and time of blood collection, after adjusting for inflammation status. Median serum Zn concentration of the population was 57.5 μg dL−1. Overall, it is estimated that 72% of the population was Zn deficient, with high prevalence in all demographic groups. Spatial statistical analysis showed that there was spatial dependence in Zn status of WRA at distances of up to 45 km. Zinc deficiency is spatially dependent over short distances. Although WRA in most areas are likely to be Zn deficient, prevalence of deficiency varies at regional scale and between rural and urban inhabitants, suggesting there is scope to explore drivers of this variation, prioritize nutritional interventions, and to design more representative surveillance programs.

Made available in DSpace on 2021-06-25T10:25:33Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-05-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Dietary zinc (Zn) deficiency is widespread globally, and is particularly prevalent in low- and middle-income countries (LMICs). Cowpea (Vigna unguiculata (L.) Walp) is consumed widely in LMICs due to its high protein content, and has potential for use in agronomic biofortification strategies using Zn. This study aimed to evaluate the effect of Zn biofortification on grain nutritional quality of 29 cowpea genotypes. Zn application did not increase cowpea yield. In 11 genotypes sucrose concentration, in 12 genotypes total sugar concentration, and in 27 genotypes storage protein concentration increased in response to Zn supply. Fifteen genotypes had lower concentrations of amino acids under Zn application, which are likely to have been converted into storage proteins, mostly comprised of albumin. Phytic acid (PA) concentration and PA/Zn molar ratio were decreased under Zn application. Six genotypes increased shoot ureides concentration in response to Zn fertilization, indicating potential improvements to biological nitrogen fixation. This study provides valuable information on the potential for Zn application to increase cowpea grain nutritional quality by increasing Zn and soluble storage protein and decreasing PA concentration. These results might be useful for future breeding programs aiming to increase cowpea grain Zn concentrations through biofortification. São Paulo State University (UNESP) São Paulo State University (UNESP), Rua Domingos da Costa Lopes 780, Jd. Itaipu Embrapa Meio-Norte School of Biosciences University of Nottingham, Sutton Bonington The James Hutton Institute, Invergowrie National Key Laboratory of Crop Genetic Improvement Huazhong Agricultural University São Paulo State University (UNESP) São Paulo State University (UNESP), Rua Domingos da Costa Lopes 780, Jd. Itaipu FAPESP: 18/18936-6 CNPq: 309380/2017-0

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

© Copyright © 2020 Zia, Ahmed, Bailey, Lark, Young, Lowe, Joy, Wilson, Zaman and Broadley. Background: Biofortification of wheat with zinc (Zn) through breeding and agronomy can reduce Zn deficiencies and improve human health. “High-Zn” wheat varieties have been released in India and Pakistan, where wheat is consumed widely as a dietary staple. The aim of this study was to quantify the potential contribution of a “high-Zn” wheat variety (Triticum aestivum L. var. Zincol-2016) and Zn fertilizers to improving dietary Zn supply under field conditions in Pakistan. Methods: Grain Zn concentration of Zincol-2016 and local reference varieties were determined at three sites of contrasting soil Zn status: Faisalabad (Punjab Province; diethylenetriamine pentaacetate- (DTPA-)extractable Zn, 1.31 mg kg−1 soil; gross plot size 13.3 m2; n = 4; reference var. Faisalabad-2008), Islamabad (Capital Territory; 0.48 mg kg−1; 4.6 m2; n = 5; reference var. NARC-2011), and Pir Sabak (Khyber Pakhtunkhwa, KPK, Province; 0.12 mg kg−1 soil; 9.1 m2; n = 4; reference vars. Pirsabak-2015, Wadhan-2017). Eight Zn fertilizer treatment levels were tested using a randomized complete block design: control; soil (5 or 10 kg ha−1 ZnSO4.H2O; 33% Zn applied at sowing); foliar (0.79 or 1.58 kg of ZnSO4.H2O ha−1 applied as a 250 L ha−1 drench at crop booting stage); three soil × foliar combinations. Results: At the Faisalabad site, the grain Zn concentration of Zincol-2016 was greater than Faisalabad-2008, with no yield penalty. Zincol-2016 did not have larger grain Zn concentrations than reference varieties used at Islamabad or Pir Sabak sites, which both had a lower soil Zn status than the Faisalabad site. Foliar Zn fertilization increased grain Zn concentration of all varieties at all sites. There were no significant effects of soil Zn fertilizers, or variety·fertilizer interactions, on grain Zn concentration or yield. Conclusions: Environment and management affect the performance of “high-Zn” wheat varieties, and these factors needs to be evaluated at scale to assess the potential nutritional impact of Zn biofortified crops. Designing studies to detect realistic effect sizes for new varieties and crop management strategies is therefore an important consideration. The current study indicated that nine replicate plots would be needed to achieve 80% power to detect a 25% increase in grain Zn concentration.

Iodine is an essential micronutrient for human health; phytofortification is a means of improving humans’ nutritional iodine status. However, knowledge of iodine uptake and translocation in plants remains limited. In this paper, plant uptake mechanisms were assessed in short-term experiments (24 h) using labelled radioisotopes; the speciation of iodine present in apoplastic and symplastic root solutions was determined by (HPLC)-ICP-QQQ-MS. Iodine storage was investigated in spinach (Spinacia oleracea L.) treated with I− and IO3−. Finally, translocation through the phloem to younger leaves was also investigated using a radioiodine (129I−) label. During uptake, spinach roots demonstrated the ability to reduce IO3− to I−. Once absorbed, iodine was present as org-I or I− with significantly greater concentrations in the apoplast than the symplast. Plants were shown to absorb similar concentrations of iodine applied as I− or IO3−, via the roots, grown in an inert growth substrate. We found that whilst leaves were capable of absorbing radioactively labelled iodine applied to a single leaf, less than 2% was transferred through the phloem to younger leaves. In this paper, we show that iodine uptake is predominantly passive (approximately two-thirds of total uptake); however, I- can be absorbed actively through the symplast. Spinach leaves can absorb iodine via foliar fertilisation, but translocation is severely limited. As such, foliar application is unlikely to significantly increase the iodine content, via phloem translocation, of fruits, grains or tubers.

Selenium (Se) is an essential element for human health and livestock productivity. Globally, human Se status is highly variable, mainly due to the influence of soil types on the Se content of crops, suggesting the need to identify areas of deficiency to design targeted interventions. In sub-Saharan Africa, including Ethiopia, data on population Se status are largely unavailable, although previous studies indicated the potential for widespread Se deficiency. Serum Se concentration of a nationally representative sample of the Ethiopian population was determined, and these observed values were combined with a spatial statistical model to predict and map the Se status of populations across the country. The study used archived serum samples (n = 3269) from the 2015 Ethiopian National Micronutrient Survey (ENMS). The ENMS was a cross-sectional survey of young and school-age children, women and men. Serum Se concentration was measured using inductively coupled plasma mass spectrometry (ICPMS). The national median (Q1, Q3) serum Se concentration was 87.7 (56.7, 123.0) &mu, g L&minus, 1. Serum Se concentration differed between regions, ranging from a median (Q1, Q3) of 54.6 (43.1, 66.3) &micro, 1 in the Benishangul-Gumuz Region to 122.0 (105, 141) &micro, 1 in the Southern Nations, Nationalities, and Peoples&rsquo, Region and the Afar Region. Overall, 35.5% of the population were Se deficient, defined as serum Se &lt, 70 &micro, 1. A geostatistical analysis showed that there was marked spatial dependence in Se status, with serum concentrations greatest among those living in North-East and Eastern Ethiopia and along the Rift Valley, while serum Se concentrations were lower among those living in North-West and Western Ethiopia. Selenium deficiency in Ethiopia is widespread, but the risk of Se deficiency is highly spatially dependent. Policies to enhance Se nutrition should target populations in North-West and Western Ethiopia.

Selenium (Se) is an essential element for human health. However, our knowledge of the prevalence of Se deficiency is less than for other micronutrients of public health concern such as iodine, iron and zinc, especially in sub-Saharan Africa (SSA). Studies of food systems in SSA, in particular in Malawi, have revealed that human Se deficiency risks are widespread and influenced strongly by geography. Direct evidence of Se deficiency risks includes nationally representative data of Se concentrations in blood plasma and urine as population biomarkers of Se status. Long-range geospatial variation in Se deficiency risks has been linked to soil characteristics and their effects on the Se concentration of food crops. Selenium deficiency risks are also linked to socio-economic status including access to animal source foods. This review highlights the need for geospatially-resolved data on the movement of Se and other micronutrients in food systems which span agriculture–nutrition–health disciplinary domains (defined as a GeoNutrition approach). Given that similar drivers of deficiency risks for Se, and other micronutrients, are likely to occur in other countries in SSA and elsewhere, micronutrient surveillance programmes should be designed accordingly.

Background Chromium (Cr) exists in the environment in two chemical forms; CrIII is an essential micronutrient for glucose and lipid metabolism, whereas CrVI is toxic and a recognised carcinogen through inhalation. Numerous studies have attempted to evaluate their transfer mechanisms from soil and solution media into plants, usually with respect to the hyperaccumulation, detoxification and tolerance of the plant to CrVI. Methods Isotopically enriched species of Cr, added as 50CrIII and 53CrVI, were used to investigate transfer from solution into the root systems of Spinacia oleracea. In addition the effect of sulphate (SO42−), as a competitor for CrVI uptake, was investigated. Separation of 50CrIII and 53CrVI was undertaken using HPLC-ICP-QQQ following isolation of root solutions using freeze/thaw centrifugation. Results Irrespective of supplied CrVI concentration (250, 500 or 1000 μg L−1), the dominant species in both apoplastic (routed through cell wall and intercellular space as a passive mechanism) and symplastic (routed through cytoplasm as an active mechanism) root solutions was CrIII. There was evidence for CrVI reduction in the rhizosphere prior to uptake as an additional detoxification mechanism. Sulphate promoted uptake of CrVI through the active pathway, although increases in SO42- concentration did not yield a proportional increase in Cr symplastic solution concentration; CrIII was also the dominant species in these root solutions. Conclusion The results indicate that Spinacia oleracea plants can effectively reduce CrVI to CrIII and that the uptake pathways for both CrIII and CrVI are more complex than previously reported. Further work is required to understand the physiological processes that result in the reduction of CrVI prior to, and during, uptake. The efficacy of sulphate to augment existing agricultural management strategies, such as liming and organic reincorporation, also requires further investigation to establish suitable application rates and applicability to other environmental contaminants.

Consumption of rice and rice products can be a significant exposure pathway to inorganic arsenic (iAs), which is a group 1 carcinogen to humans. The UK follows the current European Commission regulations so that iAs concentrations must be < 0.20 mg kg−1 in white (polished) rice and 0.1 mg kg−1 were selected for As speciation using HPLC-ICP-MS. Based on the average concentration of iAs of our samples, we calculated values for the Lifetime Cancer Risk (LCR), Target Hazard Quotient (THQ) and Margin of Exposure (MoE). We found a statistically significant difference between organically and non-organically grown rice. We also found that brown rice contained a significantly higher concentration of iAs compared to white or wild rice. Notably, 28 rice samples exceeded the iAs maximum limit stipulated by the EU (0.1 mg kg−1) with an average iAs concentration of 0.13 mg kg−1; therefore consumption of these rice types could be riskier for infants than adults. Based on the MoE, it was found that infants up to 1 year must be restricted to a maximum of 20 g per day for the 28 rice types to avoid carcinogenic risks. We believe that consumers could be better informed whether the marketed product is fit for infants and young children, via appropriate product labelling containing information about iAs concentration. Nearly half of the 55 rice samples marketed in the UK are unfit for infant food purposes, whereas iAs levels pose a minimal health risk to adults Refereed/Peer-reviewed

Made available in DSpace on 2020-12-12T01:13:32Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-03-30 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) BACKGROUND: Selenium (Se) is an essential element for humans and animals. Rice is one of the most commonly consumed cereals in the world, so the agronomic biofortification of cereals with Se may be a good strategy to increase the levels of daily intake of Se by the population. This study evaluated the agronomic biofortification of rice genotypes with Se and its effects on grain nutritional quality. Five rates of Se (0, 10, 25, 50, and 100 g ha−1) were applied as selenate via the soil to three rice genotypes under field conditions. RESULTS: Selenium concentrations in the leaves and polished grains increased linearly in response to Se application rates. A highly significant correlation was observed between the Se rates and the Se concentration in the leaves and grains, indicating high translocation of Se. The application of Se also increased the concentration of albumin, globulin, prolamin, and glutelin in polished grains. CONCLUSION: Biofortifying rice genotypes using 25 g Se ha−1 could increase the average daily Se intake from 4.64 to 66 μg day−1. Considering that the recommended daily intake of Se by adults is 55 μg day−1, this agronomic strategy could contribute to alleviating widespread Se malnutrition. © 2019 Society of Chemical Industry. São Paulo State University (UNESP) University of São Paulo (USP) School of Biosciences University of Nottingham The James Hutton Institute São Paulo State University (UNESP) FAPESP: 15/11690-3 CNPq: 309380/2017-0

Selenium (Se) is an essential human micronutrient. Deficiency of Se decreases the activity of selenoproteins and can compromise immune and thyroid function and cognitive development, and increase risks from non-communicable diseases. The prevalence of Se deficiency is unknown in many countries, especially in sub-Saharan Africa (SSA). Here we report that the risk of Se deficiency in Malawi is large among a nationally representative population of 2,761 people. For example, 62.5% and 29.6% of women of reproductive age (WRA, n = 802) had plasma Se concentrations below the thresholds for the optimal activity of the selenoproteins glutathione peroxidase 3 (GPx3; −1) and iodothyronine deiodinase (IDI; −1), respectively. This is the first nationally representative evidence of widespread Se deficiency in SSA. Geostatistical modelling shows that Se deficiency risks are influenced by soil type, and also by proximity to Lake Malawi where more fish is likely to be consumed. Selenium deficiency should be quantified more widely in existing national micronutrient surveillance programmes in SSA given the marginal additional cost this would incur.

Salt-affected soils constrain wheat production globally. A wild wheat species, Thinopyrum bessarabicum (Savul. & Rayss) Á. Löve (Poaceae), and its derivatives are tolerant of high external NaCl concentrations but have not been tested yet in field conditions. The aim of this study was to study the performance of amphidiploids derived from T. bessarabicum for grain yield (GYD), yield components and grain mineral composition traits under normal and saline soil conditions. Field experiments were conducted at Karnal (pH(water) = 7.3) and Hisar (pH(water) = 8.3) sites in 2014–2015 and 2015–2016 in India. Grain samples were analysed using inductively coupled plasma–mass spectrometry (ICP-MS). Yield and yield component traits of amphidiploids were typically greater at Karnal than Hisar. The GYD was greater at Karnal (1.6 t ha−1) than Hisar (1.2 t ha−1) in 2014–2015. However, GYD was greater at Hisar (1.7 t ha−1) than Karnal (1.1 t ha−1) in 2015–2016. Mean grain zinc (Zn) concentration of eight amphidiploids, averaged across sites and years, varied from 36 to 43 mg kg−1. Some amphidiploids derived from T. bessarabicum showed greater GYD and grain Zn concentration under saline soils (Hisar) than normal soils (Karnal). These might be potential new sources for the development of salt-tolerant wheat varieties with increased grain Zn concentration under salt-affected soils.

Biofortification with selenium (Se) may rely on rapid uptake by crops, following application, to offset progressive fixation into unavailable organic forms of Se in soil. A biofortification study was conducted on an Alfisol within a long-term conservation agriculture (CA) field trial at Chitedze Research Station, Malawi. The aim was to assess the dynamics of selenium bioavailability to a staple cereal (Zea mays) and a range of legumes (cowpeas, groundnuts, pigeon peas and velvet beans) under CA management, as well as residual Se effects in the year following biofortification. Isotopically labelled selenate (>99% enriched 77SeVI) was applied to each plot, in solution, at a rate of 20 g ha−1, at maize flowering (75 days after planting), in February 2017. Samples of grain and stover from maize and legumes, and topsoil, were collected at harvest in May 2017 and May 2018. Plant and soil samples were analyzed by ICP-MS for selenium isotopes (77Se and 78Se). The concentration of 77Se in the grain of maize and single-cropped legumes exceeded 200 µg kg−1 in all the treatments. This would contribute approximately 56–64 µg day−1 to the Malawi diet, as refined maize flour. The fertilizer derived Se concentration ratio of maize grain-to-stover Se were >1 in 2017 but

Background Dairy products provide a crucial source of dietary iodine for the majority of the UK population, contributing approximately 30–40 % of daily intake. Fluctuations in the iodine content of purchased milk both seasonally and annually implies potential fragility of iodine supply likely through fluctuating supplementation practices in cow herds. We set out to establish the level of national variation in herds and identify factors which might impact milk iodine content. Methods Milk samples were obtained from 98 herds across the UK via the National Milk Laboratories in August and December 2016. Iodine concentration of samples was measured using ICP-MS. Milk samples and feed intake data were additionally taken from 22 cows from the University of Nottingham (UON) dairy herd. Results There was considerable variation in milk iodine content from Conclusions Regional differences in milk iodine concentration between summer and winter suggests that feeding practices are far from uniform across the country. The negative association observed between iodine concentration and milk yield in UON samples, suggests that reduced summer values may be influenced by dilution in addition to seasonal differences in concentrate feed provision.

Intensive crop breeding has increased wheat yields and production in India. Wheat improvement in India typically involves selecting yield and component traits under non-hostile soil conditions at regional scales. The aim of this study is to quantify G*E interactions on yield and component traits to further explore site-specific trait selection for hostile soils. Field experiments were conducted at six sites (pH range 4.5-9.5) in 2013-14 and 2014-15, in three agro-climatic regions of India. At each site, yield and component traits were measured on 36 genotypes, representing elite varieties from a wide genetic background developed for different regions. Mean grain yields ranged from 1.0 to 5.5 t ha-1 at hostile and non-hostile sites, respectively. Site (E) had the largest effect on yield and component traits, however, interactions between genotype and site (G*E) affected most traits to a greater extent than genotype alone. Within each agro-climatic region, yield and component traits correlated positively between hostile and non-hostile sites. However, some genotypes performed better under hostile soils, with site-specific relationships between yield and component traits, which supports the value of ongoing site-specific selection activities.

Iron intakes calculated from one-day weighed records were compared with those from same day analyzed duplicate diet composites collected from 120 Malawian women living in two rural districts with contrasting soil mineralogy and where threshing may contaminate cereals with soil iron. Soils and diet composites from the two districts were then subjected to a simulated gastrointestinal digestion and iron availability in the digests measured using a Caco-2 cell model. Median analyzed iron intakes (mg/d) were higher (p

Intensive crop breeding has increased wheat yields and production in India. Wheat improvement in India typically involves selecting yield and component traits under non-hostile soil conditions at regional scales. The aim of this study is to quantify G*E interactions on yield and component traits to further explore site-specific trait selection for hostile soils. Field experiments were conducted at six sites (pH range 4.5-9.5) in 2013-14 and 2014-15, in three agro-climatic regions of India. At each site, yield and component traits were measured on 36 genotypes, representing elite varieties from a wide genetic background developed for different regions. Mean grain yields ranged from 1.0 to 5.5 t ha⁻¹ at hostile and non-hostile sites, respectively. Site (E) had the largest effect on yield and component traits, however, interactions between genotype and site (G*E) affected most traits to a greater extent than genotype alone. Within each agro-climatic region, yield and component traits correlated positively between hostile and non-hostile sites. However, some genotypes performed better under hostile soils, with site-specific relationships between yield and component traits, which supports the value of ongoing site-specific selection activities.

Background: Moringa oleifera (MO) and M. stenopetala (MS) (family Moringaceae; order Brassicales) are multipurpose tree/shrub species. They thrive under marginal environmental conditions and produce nutritious edible parts. The aim of this study was to determine the mineral composition of different parts of MO and MS growing in their natural environments and their potential role in alleviating human mineral micronutrient deficiencies (MND) in sub-Saharan Africa. Methods: Edible parts of MO (n = 146) and MS (n = 50), co-occurring cereals/vegetables and soils (n = 95) underneath their canopy were sampled from localities in southern Ethiopia and Kenya. The concentrations of seven mineral elements, namely, calcium (Ca), copper (Cu), iodine (I), iron (Fe), magnesium (Mg), selenium (Se), and zinc (Zn) in edible parts and soils were determined using inductively coupled plasma-mass spectrometry. Results: In Ethiopian crops, MS leaves contained the highest median concentrations of all elements except Cu and Zn, which were greater in Enset (a.k.a., false banana). In Kenya, Mo flowers and MS leaves had the highest median Se concentration of 1.56 mg kg-1 and 3.96 mg kg-1, respectively. The median concentration of Se in MS leaves was 7-fold, 10-fold, 23-fold, 117-fold and 147-fold more than that in brassica leaves, amaranth leaves, baobab fruits, sorghum grain and maize grain, respectively. The median Se concentration was 78-fold and 98-fold greater in MO seeds than in sorghum and maize grain, respectively. There was a strong relationship between soil total Se and potassium dihydrogen phosphate (KH2PO4)-extractable Se, and Se concentration in the leaves of MO and MS. Conclusion: This study confirms previous studies that Moringa is a good source of several of the measured mineral nutrients, and it includes the first wide assessment of Se and I concentrations in edible parts of MO and MS grown in various localities. Increasing the consumption of MO and MS, especially the leaves as a fresh vegetable or in powdered form, could reduce the prevalence of MNDs, most notably Se deficiency.

To understand the dynamic mechanisms governing soil-to-plant transfer of selenium (Se), technetium-99 (99Tc) and iodine (I), a pot experiment was undertaken using 30 contrasting soils after spiking with 77Se, 99Tc and 129I, and incubating for 2.5 years. Two grass species (Agrostis capillaris and Lolium perenne) were grown under controlled conditions for 4 months with 3 cuts at approximately monthly intervals. Native (soil-derived) 78Se and127I, as well as spiked 77Se, 99Tc and 129I, were assayed in soil and plants by ICP-MS. The grasses exhibited similar behaviour with respect to uptake of all three elements. The greatest uptake observed was for 99Tc, followed by 77Se, with least uptake of 129I, reflecting the transformations and interactions with soil of the three isotopes. Unlike soil-derived Se and I, the available pools of 77Se, 99Tc and 129I were substantially depleted by plant uptake across the three cuts with lower concentrations observed in plant tissues in each subsequent cut. Comparison between total plant offtake and various soil species suggested that 77SeO42−, 99TcO4− and 129IO3−, in soluble and adsorbed fractions were the most likely plant-available species. A greater ratio of 127I/129I in the soil solid phase compared to the solution phase confirmed incomplete mixing of spiked 129I with native 127I in the soil, despite the extended incubation period, leading to poor buffering of the spiked available pools. Compared to traditional expressions of soil-plant transfer factor (TFtotal), a transfer factor (TFavailable) expressed using volumetric concentrations of speciated ‘available’ fractions of each element showed little variation with soil properties.

Background Mineral nutrient uptake and utilisation by plants are controlled by many traits relating to root morphology, ion transport, sequestration and translocation. The aims of this study were to determine the phenotypic diversity in root morphology and leaf and seed mineral composition of a polyploid crop species, Brassica napus L., and how these traits relate to crop habit. Traits were quantified in a diversity panel of up to 387 genotypes: 163 winter, 127 spring, and seven semiwinter oilseed rape (OSR) habits, 35 swede, 15 winter fodder, and 40 exotic/unspecified habits. Root traits of 14 d old seedlings were measured in a ‘pouch and wick’ system (n = ~24 replicates per genotype). The mineral composition of 3–6 rosette-stage leaves, and mature seeds, was determined on compost-grown plants from a designed experiment (n = 5) by inductively coupled plasma-mass spectrometry (ICP-MS). Results Seed size explained a large proportion of the variation in root length. Winter OSR and fodder habits had longer primary and lateral roots than spring OSR habits, with generally lower mineral concentrations. A comparison of the ratios of elements in leaf and seed parts revealed differences in translocation processes between crop habits, including those likely to be associated with crop-selection for OSR seeds with lower sulphur-containing glucosinolates. Combining root, leaf and seed traits in a discriminant analysis provided the most accurate characterisation of crop habit, illustrating the interdependence of plant tissues. Conclusions High-throughput morphological and composition phenotyping reveals complex interrelationships between mineral acquisition and accumulation linked to genetic control within and between crop types (habits) in B. napus. Despite its recent genetic ancestry (

Urban waste disposal occurred on fenland to the west of Manchester, England, between 1900 and 1964. The reclaimed fenland, Chat Moss, is now used for mixed arable farming. A total of 1.92 Mt of waste including privy midden, street sweepings, clinkers and slaughterhouse refuse was incorporated into the moss resulting in a modified topsoil with raised pH and reduced organic matter content compared with the subsoil. Elevated levels of potentially toxic elements (PTEs) are observed in the topsoil beyond the typical depth of atmospheric contamination; Cd and As concentrations exceed soil guideline values (SGVs) at 1.8 and 43 mg/kg, respectively. Sequential extraction indicates that waste-derived Pb, Zn and Ni remain predominantly in the residual fraction, whereas Cu was mainly organically bound. Arsenic was predominately found in oxide and organic matter fractions with Cd in carbonate, oxide, organic matter and residual fractions. Pot trials indicated limited uptake of PTEs by vegetables grown on the waste-amended soil, with the exception of Cd uptake by lettuce (0.22 mg/kg FW) and Pb uptake by radish (0.16 mg/kg FW), which exceeded current EU limits of 0.2 and 0.1 mg/kg FW, respectively. Hazard quotients (HQs) identified no risks to adults from consumption of vegetables grown in these soils with the exception of lettuce consumption with a HQ of 1.4. Risks to children were slightly greater with HQs >1 for Cd in lettuce, spinach, carrots and onion, As in lettuce, parsley and onion and for Zn in spinach.

Dietary mineral deficiencies are widespread in Africa. Our previous studies in Malawi revealed population-level shortfalls in dietary calcium and selenium supply but adequate dietary magnesium (Mg) supply. Here we examine dietary Mg supply throughout Africa. Food supply data from 1961 to 2007 were compiled using Food and Agriculture Organization (FAO) Food Balance Sheets (FBSs). Magnesium supply was estimated for each country using regional food Mg composition tables. Mean Mg supply in 2007 was 649 mg capita −1 d−1, ranging from 188 mg d−1 in Eritrea to 1,828 mg d−1 in Burkina Faso. Magnesium supply was greater in West Africa than in other regions, was dominated by sorghum, maize and wheat and was correlated with calorie supply. The World Health Organization (WHO) Estimated Average Requirement (EAR) for Mg (217 mg capita −1 d−1 for adult males) was exceeded in most countries. Using the EAR cut-point method, the risk of dietary Mg deficiency in Africa is

The environmental fate and possible residual effects of applied selenium (Se) are important issues when considering sustainable biofortification of food crops to improve human health. Our objectives were to assess residual effects of Se biofortification of maize in Malawi using a combination of 74 Se-labelling studies and measurements of KH 2 PO 4 -extractable soil Se. Stable 74 Se isotope trials showed recovery rates in maize grain of 6.5 and 10.8% from 10 g Se ha −1 applied to two contrasting sites, Chitedze and Mbawa; the 74 Se label comprised 69 and 81% of the grain Se content respectively. However, in the following ‘residual’ year, only 2.0 and 0.78% of Se uptake in grain came from the 74 Se-labelled fertiliser originally applied, amounting to −1 ) at six sites across Malawi varied with soil type but comprised 3.5 and 4.8% of that applied, at Chitedze and Mbawa respectively. However, a second maize crop grown in the same plots in the following cropping season accessed only 0.23 and 0.19% of the original Se application, constituting less than 5% of the phosphate-extractable fertiliser Se measured in the soil at harvest in the previous (fertilised) year. Thus, residual benefits from Se application were measureable but extremely small, probably due to rapid loss of soluble selenate after application or fixation into unavailable organic forms.

Suboptimal dietary Se intake is widespread in Malawi due to low levels of plant-available Se in most soils and narrow food choices. The aim of this study was to determine the potential for biofortifying maize using Se-enriched fertilisers in Malawi. The response of maize to three forms of selenate-Se fertiliser was determined. Crops were treated with a liquid drench of Na2SeO4(aq) (0–100 g Se ha−1), a compound NPK + Se fertiliser (0–6 g Se ha−1), or Se-enriched calcium ammonium nitrate (CAN + Se; 0–20 g Se ha−1). Experiments with Na2SeO4(aq) and NPK + Se were conducted at six field sites, and at a subset of three sites with CAN + Se, in 2008/09 and 2009/10 (i.e. 30 experimental units). The increase in grain Se concentration was approximately linear for all Se forms and application rates (R2 > 0.90 for 27 of the 30 experimental units). On average, whole-grain Se increased by 20, 21 and 15 μg Se kg−1for each gram of Se applied as Na2SeO4(aq), NPK + Se and CAN + Se, respectively. Grain and stover yields were unaffected by Se applications. An application of 5 g Se ha−1 to maize crops in Malawi would increase dietary Se intake by 26–37 μg Se person−1 d−1 based on national maize consumption patterns. Agronomic biofortification with Se in Malawi is feasible in theory through the existing national Farm Input Subsidy Programme (FISP) if deemed to be economically and politically acceptable.

Background and Aims Selenium (Se) is an essential nutrient for humans and animals. In order to ensure an optimal concentration of Se in crops, Se fertilisers are applied. Catch crops may be an alternative way to increase Se concentrations in vegetables. Methods Three experiments in Denmark between 2007–10 investigated the ability of catch crops (Italian ryegrass, fodder radish and hairy vetch) under different fertiliser regimes to reduce soil Se content in the autumn and to increase its availability in spring to the succeeding crop. Results and Conclusions The catch crops (Italian ryegrass and fodder radish) increased water-extractable Se content in the 0.25–0.75msoil layer in only one of the experiments. Selenium uptake by the catch crops varied between 65 and 3263 mg ha−1, depending on species, year and fertilisation treatment; this corresponded to 0.1–3.0% of the water-extractable soil Se content. The influence of catch crops on Se concentrations and uptake in onions and cabbage was low. There was a decrease in Se uptake and recovery of applied Se by onions following catch crops, which might indicate Se immobilisation during catch crop decomposition.

Evidence of chloride-enhanced cadmium uptake by plants in soil experiments has been reported. However, it is still unclear whether this finding is due to increased rates of Cd2+ diffusion to plant roots or the direct uptake of complexes such as CdC1+. A controlled hydroponic experiment was undertaken to distinguish and quantify the uptake rates of free and inorganic-complexed cadmium and to model the uptake of cadmium by Indian mustard plants with a 'biotic ligand model'. Plants were treated with NaCl (0 to 200 mM) including equivalent Na2SO4 treatments. Cadmium speciation in solution was calculated using the WHAM-VI model. Results of the current trials showed that higher Cl-concentrations in solution generally resulted in greater cadmium accumulation by plants than predicted by the Cd2+ activity. Activities of Cd-chloro complexes showed the best correlations with the cadmium concentrations in the plants compared with the activity of Cd2+. The biotic ligand model showed a reasonable good fit for the plants when assuming competition by Cd2+ and CdCl+ for sorption sites at root level. The relative values of the two reaction constants suggest that root affinity for Cd2+ is 3.4 times greater than for CdCl+. Nevertheless this clearly indicates a substantial role for chloro-complexed cadmium accumulation.

The aim of this study was to characterise nutritional-I status in Malawi. Dietary-I intakes were assessed using new datasets of crop, fish, salt and water-I concentrations, while I status was assessed for 60 women living on each of calcareous and non-calcareous soils as defined by urinary iodine concentration (UIC). Iodine concentration in staple foods was low, with median concentrations of 0.01 mg kg−1 in maize grain, 0.008 mg kg−1 in roots and tubers, but 0.155 mg kg−1 in leafy vegetables. Freshwater fish is a good source of dietary-I with a median concentration of 0.51 mg kg−1. Mean Malawian dietary-Iodine intake from food, excluding salt, was just 7.8 μg d−1 compared to an adult requirement of 150 μg d−1. Despite low dietary-I intake from food, median UICs were 203 μg L−1 with only 12% defined as I deficient whilst 21% exhibited excessive I intake. Iodised salt is likely to be the main source of dietary I intake in Malawi; thus, I nutrition mainly depends on the usage and concentration of I in iodised salt. Drinking water could be a significant source of I in some areas, providing up to 108 μg d−1 based on consumption of 2 L d−1.

With the release of the Department for the Environment, Food and Rural Affairs/Advisory Committee on Animal Feed Guidance Note for Supplementing Copper to Bovines it was noted that the current copper status of the national herd was not known. Liver samples were recovered from 510 cull cattle at a single abattoir across a period of three days. The samples were wet-ashed and liver copper concentrations determined by inductively coupled plasma mass spectrometry analysis. Breed, age and previous location information were obtained from the British Cattle Movement Service. Dairy breeds had higher liver copper concentrations than beef breeds. Holstein-Friesian and ‘other’ dairy breeds had 38.3 per cent and 40 per cent of cattle above the Animal Health and Veterinary Laboratories Agency (AHVLA) reference range (8000 µmol/kg dry matter), respectively, whereas only 16.9 per cent of animals in the combined beef breeds exceeded this value. It was found that underlying topsoil copper concentration was not related to liver copper content and that age of the animal also had little effect on liver concentration. In conclusion, over 50 per cent of the liver samples tested had greater-than-normal concentrations of copper with almost 40 per cent of the female dairy cattle having liver copper concentrations above the AHVLA reference range, indicating that a significant proportion of the UK herd is at risk of chronic copper toxicity.

Background In this review, we examine the potential of Zn-enriched fertilisers to alleviate human dietary Zn deficiency. The focus is on ten African countries where dietary Zn supply is low and where fertiliser subsidies are routinely deployed on cereal crops. Scope Dietary Zn supply and deficiency prevalence were quantified from food supply and composition data. Typical effects of soil (granular) and foliar Zn applications on Zn concentrations in maize (Zea mays L.), rice (Oryza sativa L.) and wheat (Triticum aestivum L.) grains were based on a systematic literature review. Reductions in disease burdens attributable to Zn deficiency and cost-effectiveness were estimated using a disability-adjusted life years (DALYs) approach. Conclusions Baseline Zn supply in 2009 ranged from 7.1 (Zambia) to 11.9 (Mali) mg capita−1 day−1; prevalence of Zn deficiency ranged from 24 (Nigeria) to 66 % (Zambia). In reviewed studies, soil Zn application led to an increase in median Zn concentration in maize, rice and wheat grains of 23, 7 and 19 %; foliar application led to increases of 30, 25 and 63 %. Enriching granular fertilisers within current subsidy schemes would be most effective in Malawi, reducing DALYs lost due to Zn deficiency by 10 %. The cost per DALY saved ranged from US$ 624 to 5893 via granular fertilisers and from US$ 46 to 347 via foliar fertilisers. Foliar applications are likely to be more cost effective than soil applications due to fixation of Zn in the soil but may be more difficult to deploy. Zinc fertilisation is likely to be less cost-effective than breeding in the longer term although other micronutrients such as selenium could be incorporated.

Short rotation coppice (SRC) such as Salix spp. can be grown as an energy crop and offers some potential for economic and practical phytoextraction of marginally contaminated arable soil. This study tested various soil amendments intended to increase soil metal availability to Salix, investigated the distribution of metal between different tree fractions and assessed the viability of phytoextraction using SRC on arable soils. Several Salix genotypes were grown in field trials over 4 years. Cd and Zn concentrations were generally ranked in the order leaves > bark > wood. Metal concentrations in wood increased towards the top of the willow stems, whereas concentrations in leaves showed the opposite trend. None of the amendments significantly increased uptake of Zn by willow. However, in response to a range of soil HCl treatments, mean Cd concentrations in stems and leaves were 112% and 130% of control values. Data from the current experiment, and previous studies, were combined to develop a predictive model of Cd and Zn stem uptake by Salix. The minimum biological concentration factor (BCF) required to achieve a prescribed soil metal target was also calculated based on typical proportions of bioavailable Cd in sludge-amended soils for a 25-year Salix rotation. The best Salix genotypes investigated achieved less than 20% of the uptake rate required to remove one third of the soil Cd content (equivalent to the average isotopically exchangeable Cd fraction in soils at the study site).

MBL-MEL, a simple model of ecosystem biogeochemistry, is amended and applied to plant and soil C, 14N and 15N data for the summers of 2001–2003 from Brandalpynten, a maritime high Arctic site on Svalbard following the application of 15N (99 atom%) as 15NO3-N at or 15NH4-N at concentrations of 1 or 5 kg N ha−1. Variants of this Parent model are also developed to incorporate: temperature dependence into equations describing nutrient fluxes (Temp model); cryptogams (Cryp model); both features combined (CrypTemp model). Goodness-of-fit (GOF) statistics suggest that the addition of temperature-dependence improves the utility of models with and without cryptogams: the residual weighted sums of squares per data point were 5.69, 3.91, 4.31 and 3.93 for the Parent, Temp, Cryp and CrypTemp models respectively. The application of model selection criteria confirm that the addition of temperature-dependence also improves model generalisability. Across all models, the principal discrepancies between observation and prediction are associated with the inorganic soil 15N pool. We conclude that models in which fluxes are described using simple equations that can be augmented to include additional complexity, are an ideal starting point from which the relationship between GOF and model generalisability can be assessed.

Summary • Here, we examined uptake of radio-labile cadmium (Cd) by arbuscular mycorrhizal (AM) fungi from topsoil historically contaminated by Cd, lead (Pb) and zinc (Zn) from mine-spoil. • Using compartmented pots, Plantago lanceolata plants were grown with or without AM inoculum, isolated from the same soil as used in the experiment. Uptake of radio-labile Cd was determined from the specific activity in the host plant and measured radio-labile Cd pool in the soil. • Specific activity of 109 Cd in plant shoots showed that 10% of the Cd uptake occurred through AM fungal hyphae. Cd concentrations were greatest in the roots of mycorrhizal plants and the shoots of nonmycorrhizal plants, possibly indicating fungal immobilisation of Cd within the mycorrhiza. • The method presented here allows discrimination between Cd uptake by roots and hyphae in individual plants.

Wheat is an important dietary source of zinc (Zn) and other mineral elements in many countries. Dietary Zn deficiency is widespread, especially in developing countries, and breeding (genetic biofortification) through the HarvestPlus programme has recently started to deliver new wheat varieties to help alleviate this problem in South Asia. To better understand the potential of wheat to alleviate dietary Zn deficiency, this study aimed to characterise the baseline effects of genotype (G), site (E), and genotype by site interactions (GxE) on grain Zn concentration under a wide range of soil conditions in India. Field experiments were conducted on a diverse panel of 36 Indian-adapted wheat genotypes, grown on a range of soil types (pH range 4.5-9.5), in 2013-14 (five sites) and 2014-15 (six sites). Grain samples were analysed using inductively coupled plasma-mass spectrometry (ICP-MS). The mean grain Zn concentration of the genotypes ranged from 24.9-34.8 mg kg-1, averaged across site and year. Genotype and site effects were associated with 10% and 6% of the overall variation in grain Zn concentration, respectively. Whilst G x E interaction effects were evident across the panel, some genotypes had consistent rankings between sites and years. Grain Zn concentration correlated positively with grain concentrations of iron (Fe), sulphur (S), and eight other elements, but did not correlate negatively with grain yield, i.e. no yield dilution was observed. Despite a relatively small contribution of genotype to the overall variation in grain Zn concentration, due to experiments being conducted across many contrasting sites and two years, our data are consistent with reports that biofortifying wheat through breeding is likely to be effective at scale given that some genotypes performed consistently across diverse soil types. Notably, all soils in this study were probably Zn deficient and interactions between wheat genotypes and soil Zn availability/management (e.g. the use of Zn-containing fertilisers) need to be better-understood to improve Zn supply in food systems.

The hyperaccumulator Thlaspi caerulescens was grown with Hordeum vulgare and Lepidium heterophyllum in a split pot experiment to examine the effect of rhizosphere interactions on metal uptake. The objective was to assess the viability of such intercropping as either (1) a system of ‘phytoprotection’ for nonaccumulating plants or (2) a means of enhancing phytoextraction with large-biomass crops through increased metal mobilization within the shared rhizosphere. The plants were separated by (1) an impermeable barrier, (2) a permeable root barrier, or (3) no physical barrier to allow different degrees of root interaction. Studies of rhizosphere effects using split pot experiments are subject to considerable uncertainty by the need to relate test results to appropriate control plants. This was resolved by comparing plant metal concentrations to ‘equivalent’ control plants, with the same yield, based on the observed variation in metal concentration with yield under similar growing conditions. Cadmium ...

Moringa oleifera (MO) and M. stenopetala (MS) are two commonly cultivated species of the Moringaceae family. Some households in southern Ethiopia (S. ETH) and Kenya (KEN) plant MS and MO, respectively. The edible parts of these species are rich in amino acids, vitamins and minerals, especially selenium. Despite their nutritional value, Moringa is sometimes considered as a "famine food". The aim of this study was to determine the extent of dietary utilization of these plants by Moringa Growing Households (MGHs). Moringa growing households were surveyed in 2015. Twenty-four and 56 heads of MGHs from S. ETH and KEN, respectively, were interviewed using semi-structured questionnaires. Subsistence agriculture was the main source of livelihood for all MGHs in S. ETH and 71% of those in KEN. All MGHs in S. ETH cultivated MS while those in KEN cultivated MO. Of the MGH heads in S. ETH, 71% had grown MS as long as they remember; the median cultivation period of MO in KEN was 15 years. All MGHs in S. ETH and 79% in KEN used Moringa leaves as a source of food. Forms of consumption of leaves were boiled fresh leaves, and leaf powder used in tea or mixed with other dishes. Other uses of Moringa include as medicine, fodder, shade, agroforestry, and as a source of income. Although MO and MS have multiple uses, MGHs face several challenges, including a lack of reliable information on nutritional and medicinal values, inadequate access to markets for their products, and pest and disease stresses to their plants. Research and development to address these challenges and to promote the use of these species in the fight against hidden hunger are necessary.

In the current study, potential involvement of anthocyanins in the defence of the Zn hyperaccumulator plant, Noccaea caerulescens, was investigated in two independent glasshouse experiments. Plants were grown in compost amended with a range of Zn concentrations. In the first experiment, foliar herbivory was simulated by clipping the shoots with scissors, whilst in second experiment, plants were subjected to natural herbivory by thrips (Frankliniella occidentalis). In both experiments, foliar Zn concentrations were approximately twice as high as that applied to the soil, indicating accumulation occurred. In the clipping experiment, foliar anthocyanin concentrations decreased by 22–45 % with increasing soil Zn amendments and clipping increased anthocyanin concentrations by 17–24 % relative to unclipped plants. In a thrips feeding experiment, Zn treatment had little effect on anthocyanin content although there was a trend towards increased anthocyanin production in plants grown at the lower concentrations of Zn. Anthocyanin concentration increased by 49–52 % in N. caerulescens leaves subjected to thrip attack compared to that of thrip-free shoots. Thus, anthocyanins increased as a result of foliar damage (manual clipping and natural herbivory) and generally decreased with enhanced Zn concentrations. Foliar glucosinolate concentrations were higher in ungrazed leaves than in grazed leaves of the same thrip-infested plants, whilst anthocyanin production was higher in the grazed leaves. The possibility of an interaction between glucosinolate and anthocyanin production resulting from herbivory is discussed.

The Zn hyperaccumulating plant, Noccaea caerulescens , was grown under controlled conditions at a range of Zn concentrations (0–1000 mg kg − 1 dwt. soil) to determine the effectiveness of hyperaccumulation in deterring the cabbage whitefly, Aleyrodes proletella , and to establish the relationship between levels of foliar Zn and glucosinolates (organic defence compounds). Two weeks after introducing A. proletella adults to the plants, next generation nymphs were quantified. This sucking insect caused minimal damage to plant tissue and did not affect foliar glucosinolate levels. Foliar Zn concentrations increased with increasing soil Zn application and reached a maximum of ~ 7000 mg kg − 1 . More whitefly nymphs were observed on plants as the foliar Zn concentration increased (up to ~ 3000 mg kg − 1 ) after which numbers declined. Zn was an explanatory variable in accumulated generalised linear regression after the variation in the data due to C/N ratio had been accounted for. Nymph numbers declined with increasing C/N ratio and increased with increasing N concentration. The highest glucosinolate concentrations were in shoots with the lowest Zn concentrations; this is consistent with the ‘trade-off’ hypothesis which states that elemental defence mechanisms allow for lowered organic defences.

Mineral malnutrition is widespread in sub-Saharan Africa but its extent is difficult to quantify. Using Malawi as a case study, the aim of this work was to investigate the adequacy of calcium (Ca) and magnesium (Mg) nutrition by combining national food supply and food composition data with a new spatial survey of maize grain. Non-maize dietary sources of Ca and Mg were estimated using existing food supply and composition data. Calcium and Mg concentrations in maize grain were determined at 88 field sites, representing > 75 % of Malawi’s land area in terms of soil classification. Median maize grain concentrations from the survey were 34 and 845 mg kg-1, representing a per capita supply of 12 and 299 mg d-1 of Ca and Mg, respectively. Combining these data with food supply and composition data reveals that average Ca nutrition is likely to be inadequate for many individuals, whereas average Mg nutrition appears adequate. Optimal supply of Ca per capita depends critically on balanced food availability and choice. Since maize grain sourced from highly calcareous soils is still unlikely to deliver > 5 % of estimated average requirements, agronomic solutions to rectify Ca malnutrition via maize are limited, in comparison with strategies for dietary diversification.

Selenium (Se) is an essential human micronutrient with critical roles in immune functioning and antioxidant defence. Estimates of dietary Se intakes and status are scarce for Africa although crop surveys indicate deficiency is probably widespread in Malawi. Here we show that Se deficiency is likely endemic in Malawi based on the Se status of adults consuming food from contrasting soil types. These data are consistent with food balance sheets and composition tables revealing that >80% of the Malawi population is at risk of dietary Se inadequacy. Risk of dietary Se inadequacy is >60% in seven other countries in Southern Africa, and 22% across Africa as a whole. Given that most Malawi soils cannot supply sufficient Se to crops for adequate human nutrition, the cost and benefits of interventions to alleviate Se deficiency should be determined; for example, Se-enriched nitrogen fertilisers could be adopted as in Finland.

Selenium is an essential element in human diets but the risk of suboptimal intake increases where food choices are narrow. Here we show that suboptimal dietary intake (i.e. 20-30 µg Se person(-1) d(-1)) is widespread in Malawi, based on a spatial integration of Se concentrations of maize (Zea mays L.) grain and soil surveys for 88 field sites, representing 10 primary soil types and75% of the national land area. The median maize grain Se concentration was 0.019 mg kg(-1) (range 0.005-0.533), a mean intake of 6.7 µg Se person(-1) d(-1) from maize flour based on national consumption patterns. Maize grain Se concentration was up to 10-fold higher in crops grown on soils with naturally high pH (6.5) (Eutric Vertisols). Under these less acidic conditions, Se becomes considerably more available to plants due to the greater solubility of Se((IV)) species and oxidation to Se((VI)).

The uptake of lead by two contrasting plant species, radish and red fescue, grown in soils contaminated by mine spoil was investigated. Uptake was found to be poorly correlated either with pH or total Pb concentration in the soils. By contrast, a good correlation was obtained, particularly for red fescue, between Pb uptake and Pb concentration in the solution of equilibrated soil suspensions over a wide range of soil pH, total soil Pb and soil solution Pb concentration. Calculations suggested a similar order of magnitude in the total amounts of Pb taken up by the plants and Pb in the soil solution of the root zone, justifying the latter as a good index of Pb-availability. ei]Section editor: A C Borstlap