Effect of drought and elevated temperature on grain zinc and iron concentrations in CIMMYT spring wheat

Abiotic stress caused by increasing temperature and drought is a major limiting factor for wheat productivity around the world. Wheat plays an important role in feeding the world, but climate change threatens its future harvest and nutritional quality. In this study, grain iron (Fe) and zinc (Zn) concentrations of 54 wheat varieties, including CIMMYT derived historic and modern wheat varieties grown in six different environmental conditions, were analyzed. The objective of the study was to evaluate the effect of water and heat stress on the nutritional value of wheat grains with a main emphasis on grain protein content, Zn and Fe concentrations. Significant effects of environment on protein content and grain micronutrients concentration were observed. The protein and Zn concentrations increased in the water and heat stressed environments, whereas Zn and Fe yield per unit area was higher in non-stress conditions. The results suggest that genetic gains in the yield potential of CIMMYT derived wheat varieties have tended to reduce grain Zn, in some instances; however, environmental variability might influence the extent to which this effect manifests itself.     

Localisation of iron in wheat grain using high resolution secondary ion mass spectrometry

Insufficient iron (Fe) is one of the most prevalent micronutrient deficiencies in humans, with billions of people affected. Cereal grains are an important source of Fe for humans but the bioavailability of Fe in cereals is generally low. Information regarding the cellular and sub-cellular localisation of Fe in wheat grain will aid optimising nutrient delivery for human health. In this study high resolution secondary ion mass spectrometry (NanoSIMS) was used to map the distribution of Fe in the aleurone layer and in the endosperm of immature wheat grain. Iron was shown to be localised strongly in the phytin globoids in the aleurone cells and to a lesser extent in the cytoplasm around the starch granules in the endosperm.     

Improved nitrogen status enhances zinc and iron concentrations both in the whole grain and the endosperm fraction of wheat

This study was conducted to assess the role of increasing N supply in enrichment of whole grain and grain fractions, particularly the endosperm, with Zn and Fe in wheat. The endosperm is the most widely consumed part of wheat grain in many countries. Plants were grown in the greenhouse with different soil applications of N and Zn and with or without foliar Zn spray. Whole grain and grain fractions were analyzed for N, P, Zn and Fe. Increased N supply significantly enhanced the Zn and Fe concentrations in all grain fractions. In the case of high Zn supply, increasing N application enhanced the whole grain Zn concentration by up to 50% and the endosperm Zn by over 80%. Depending on foliar Zn supply, high N elevated the endosperm Fe concentration up to 100%. High N also generally decreased the P/Zn and P/Fe molar ratios in whole grain and endosperm. The results demonstrate that improved N nutrition, especially when combined with foliar Zn treatment, is effective in increasing Zn and Fe of the whole grain and particularly the endosperm fraction, at least in the greenhouse, and might be a promising strategy for tackling micronutrient deficiencies in countries where white flour is extensively consumed.     

Biofortification strategies to increase grain zinc and iron concentrations in wheat

Micronutrient deficiencies, especially those arising from zinc (Zn) and iron (Fe), pose serious human health problems for more than 2 billion people worldwide. Wheat is a major source of dietary energy and protein for the world's growing population, and its potential to assist in reducing micronutrient-related malnutrition can be enhanced via integration of agronomic fertilization practices and delivery of genetically-manipulated, micronutrient rich wheat varieties. Targeted breeding for these biofortified varieties was initiated by exploiting available genetic diversity for Zn and Fe from wild relatives of cultivated wheat and synthetic hexaploid progenitors. The proof-of-concept results from the performance of competitive biofortified wheat lines showed good adaptation in target environments without compromising essential core agronomic traits. Agronomic biofortification through fertilizer approaches could complement the existing breeding approach; for instance, foliar application of Zn fertilizer can increase grain Zn above the breeding target set by nutritionists. This review synthesizes the progress made in genetic and agronomic biofortification strategies for Zn and Fe enrichment of wheat.     

Phytate and mineral elements concentration in a collection of Italian durum wheat cultivars

Mineral deficiencies are prevalent in human populations and the improvement of the mineral content in cereal products represents a possible strategy to increase the human mineral intake. Nevertheless, most of the inorganic phosphorus (P_i) present in mature cereal seeds (40–80%) is stored as phytate, an anti-nutritional factor that forms complexes with minerals such as Ca, Mg, Zn and Fe reducing their bioavailability. The present study was undertaken: (i) to determine the variation in phytate and mineral concentrations in the whole grains of 84 Italian durum wheat (Triticum durum Desf.) cultivars representative of old and modern germplasm; (ii) to estimate the magnitude of genotype × environment interaction effects; and (iii) to examine the interrelationships among mineral concentrations in durum wheat with the final aim to identify superior durum wheat cultivars that possess low phytate content and high concentration of mineral elements in their whole-wheat flour. The cultivars were grown in field trials during 2004–2005 at Foggia, Italy and during 2005–2006 at Foggia and Fiorenzuola d’Arda—Southern and Northern Italy. The phytate content was estimated indirectly by using a microtitre plate assay evaluating the P_i absorbance at 820 nm, while the Cu, Fe, Mn, Ca, K, Mg, Na and Zn mineral contents were determined by ICP/OES. The contents of Zn and Fe across years and locations ranged from 28.5 to 46.3 mg/kg for Zn with an average of 37.4 mg/kg and from 33.6 to 65.6 mg/kg for Fe with an average of 49.6 mg/kg. P_i grain content was between 0.46 and 0.76 mg/g showing a positive correlation with all minerals except Cu and Zn. Although breeding activity for Fe and Zn would be difficult because G × E interaction is prevalent, multi-location evaluation of germplasm collection help to identify superior genotypes to achieve this objective. The results here reported open the possibility of designing a specific breeding program for improving the nutritional value of durum wheat through the identification of parental lines with low-P_i and high minerals concentration in whole grains.     

Phytase activity in extracts of flour and bran from wheat cultivars: enhanced extractability with β-glucanase and endo-xylanase

Phytase (EC 3.1.3.8) hydrolyzes phytic acid to myo-inositol and inorganic phosphate through intermediate myo-inositol phosphates. Microbial phytase has been employed to minimize the negative effects of phytic acid in cereal-based feeds, however, other sources such as wheat, would be natural alternatives. Investigations were therefore carried out to determine the levels of phytase activity in various cultivars and how the extraction of the enzyme may be enhanced using buffers fortified with glycanases. We screened 23 cultivars and the results showed that bran from hard white wheat cultivars had relatively lower levels of activity, ranging from about 1.5 to about 2.5 FTU/g bran, whereas hard red wheat cultivars had much higher levels, ranging from approximately 2 to 5.5 FTU/g bran. These levels were greatly enhanced, up to 5-fold, when extraction buffer contained a commercial preparation consisting of β-glucanase (EC 3.2.1.6) and endo-xylanase (EC 3.2.1.8) (Natugrain) (opt 1%) from BASF. The effect of glycanases was concentration and cultivar dependent, but not significantly influenced by temperature exposure of mixtures of samples with extraction buffers prior to extraction. Relative increases were more substantial in hard white than in hard red wheat cultivars. The additional value of supplementing grain-based diets with glycanases for monogastric animals is discussed.     

<Emphasis Type="Italic">Pulque</Emphasis>, An Alcoholic Drink from Rural Mexico,Contains Phytase. Its <Emphasis Type="Italic">in vitro</Emphasis> Effects on Corn Tortilla

Pulque is made by fermenting the agave sap or aguamiel of Agave atrovirens with a whole array of microorganisms present in the environment including several lactic acid bacteria and yeasts such as Saccharomyces cerevisiae. Ascorbic acid was determined in pulque and aguamiel, respectively. Phytase activity in lees, liquid and freeze-dried pulque was assayed by measuring the appearance of phosphate from phytate by a colorimetric method likewise phosphate from phytate present in fresh corn tortilla was measured after in vitro incubation with pulque. Iron, zinc, calcium, magnesium and selenium contents were measured in pulque and corn tortilla as well as in nixtamalized corn flour (NCF), the latter is used to make instant tortilla, since corn provides most of the energy as well as most of the phytate in the Mexican rural diet. Pulque showed phytase activity but much less ascorbic acid and iron than previously reported; additionally, phytase in pulque hydrolyzed most of phytate’s corn tortilla. Lees, which is mostly made of pulque’s microbiota, significantly accumulated iron and zinc but no selenium. NCF was fortified with iron by the manufacturers but poorly blended. There were significant differences on selenium content between tortillas samples, apparently some soils in central Mexico are selenium deficient. Moderate pulque intake appears to increase the bioavailability of iron and zinc bound by phytate in corn.     

Influence of vegetative cycle of asparagus (Asparagus officinalis L.) on copper,iron, zinc and manganese content

The essential elements copper (Cu), iron (Fe), zinc (Zn) and manganese (Mn) were analyzed in fresh asparagus to determine the effects of the vegetative cycle of the plant on the micronutrient content. Asparagus samples were classified in two groups by diameter (<11 mm and >14 mm). Asparagus from a sample group with the same diameter were divided into two portions (apical and basal) according to distance from the tip. The concentrations of copper, iron, zinc and maganese increased during the vegetative cycle of the asparagus, mainly in the apical portion which showed significantly greater concentrations with respect to the basal portion. The >14 mm diameter asparagus presented higher levels of copper, zinc and manganese, whereas the concentration of iron was greater in the <11 mm diameter asparagus. The mean element levels were (mg/kg dry weight): Cu, 18.9±3.9; Fe, 91.7±33.7; Zn, 69.5±24.6 and Mn, 20.9±5.0).     

Phytic acid content and “in vitro” iron, calcium and zinc bioavailability in bakery products: The effect of processing

Whole-grain bakery products and cereals are valuable sources of dietary fiber, vitamins, and trace elements. However, the presence of phytate, could decreases mineral bioavailability due to its chelating properties. In this study, the effect of fermentation and baking on the phytate content of different bakery products was measured by HPLC; the mineral availability in bakery products during processing was investigated by measuring solubility and dialysis, as well as the mineral uptake and transport by Caco-2 cells after in vitro digestion. Raw materials showed the highest amount of phytate, causing an important effect on the stage of processing. The solubility and dialyzability of iron increased with fermentation, meanwhile calcium and zinc showed a high variability depending on the product analyzed. After baking, the dialyzability of minerals increased with respect to the fermented dough in most cases. The highest uptake and transport efficiency of iron and calcium in cells corresponded to dough after fermentation of wheat flour with respect to the baked samples. For zinc, no differences were observed between fermented dough and after baking on uptake and transport efficiencies. This study showed that in vitro mineral availability of bakery products is influenced by the stage of processing and ingredients used.     

Response of common wheat varieties to organic and conventional production systems across Italian locations,and implications for selection

Specific breeding for organic systems may help reduce their yield gap relative to conventional systems by exploiting genotype × system (GS) interaction. Likewise, specific breeding for distinct subregions within a region could capitalize on genotype × location (GL) interaction. Grain yield and test weight of common wheat varieties were evaluated under organic and conventional systems in ten locations spanning from northern to southern Italy, with the objectives of: (i) comparing production systems; (ii) investigating the extent of GS and GL interactions and their relationship with genotypic and environmental characteristics; and (iii) preliminarily comparing, in terms of predicted selection gains, different strategies to cope with GS and GL effects. These effects were investigated in the 2-year Data set 1 including seven genotypes. GS effects were also assessed in the annual Data sets 2 and 3 including 13 and 11 genotypes, respectively. The yield reduction of organic systems relative to conventional ones averaged 28% in Data set 1, 29% in Data set 2 and 14% in Data set 3. Organic systems also tended to a modest test weight reduction. Genetic correlations between systems ranged from high to very high (0.88 ≤ r_g ≤ 0.98) for yield and test weight, owing to nil or limited GS interaction. Broad-sense heritability tended to be higher in conventional systems than organic ones for yield in two data sets (mainly due to lower experimental error) while being similar in the two systems in the other cases. Predicted selection gains suggested nil (yield) or very modest (test weight) advantage of direct selection in organic systems relative to indirect selection in conventional systems, when targeting organic systems. The scope for selection only in conventional systems was reinforced when comparing predicted gains for selection scenarios which target both systems in relation to their foreseeable marketing importance. GL effects for yield and test weight were significant and were modeled by additive main effects and multiplicative interaction analysis. Site classification based on GL effects for yield revealed a larger subregion A including northern and central Italy and a smaller subregion B comprising southern Italy, accordingly with previous, independent studies. Yield selection only in subregion A (with indirect selection gain for subregion B) implied slightly higher predicted gain for A (+4%) and much lower gain for B (−24%) relative to independent, direct selection in each subregion. Selection for specific geoclimatic subregions may have greater importance than selection for specific production systems.     

Nutritive value of soybean,rapeseed and wheat proteins,and various blends of these vegetable proteins and their fractions in rats

Blends of vegetable proteins were prepared to improve the nutritive value of these proteins. Soybean flour, rapeseed protein concentrate, whole wheat flour, soybean 2S+11S extract, wheat albumin-globulin + glutenin (AG+G) functions, and some of their blends were compared to casein for protein efficiency ratio (PER) and apparent digestibility coefficient (ADC). Autoclaving (1 h) soybean proteins was also studied. Casein and rapeseed protein concentrate gave the highest weight gains and PER. Other protein sources gave lower values for both PER (P<0.05) and weight gain. The digestibility of all vegetable proteins was lower (P<0.05) than that of casein. PER of soybean 2S+11S extract was significantly lower (P<0.05) than that of soybean flour. Autoclaving significantly (P<0.05) improved the PER of both soybean flour and 2S+11S extract. The ADC of autoclaved 2S+11S extract was similar (P<0.05) to that of autoclaved soybean flour and significantly higher (P<0.05) than that of 2S+11S extract. Soybean flour had the lowest (P<0.05) ADC. Heat treatment destroyed antinutritional factors, probably trypsin inhibitors and/or haemagglutinins of soybean. This was accompanied by improvement in the nutritional value of protein. The four blends were chosen on the basis of amino acid composition, chromatography of proteolyzates and nutritive value of each fraction. The PER of wheat albumin-globulin and glutenin (AG+G) blend was similar (P<0.05) to that of wheat flour and lower (P<0.05) than that of all other blends used. Wheat AG+G+rapeseed protein concentrate and wheat AG+G+soybean flour blends gave the highest (P<0.05) PER. Wheat AG+G improved the PER of 2S+11S extract and of soybean flour but decreased the PER of rapeseed protein concentrate. Wheat AG+G and wheat AG+G+rapeseed protein concentrate blends gave an ADC significantly higher (P<0.05) than that of wheat AG+G blend containing soybean flour of 2S+11S extract. However, blending wheat AG+G with either 2S+11S extract of soybean flour improved ADC.     

Effects of region and cultivar on alkylresorcinols content and composition in wheat bran and their antioxidant activity

This study evaluated the effects of cultivar and region on the composition of alkylresorcinols (ARs) of 24 wheat bran samples from 6 cultivars grown in four locations (Bath, Nairn, Palmerstone and Ridgetown) in Ontario (ON), Canada, using gas chromatography/mass spectrometry (GC/MS). Total phenolic content (TPC) of wheat bran extracts was determined by the Folin–Ciocalteau method and the antioxidant activity of wheat bran extracts was measured by 2, 2-Dipheny-1-picryhydrazyl radical (DPPH) scavenging activity and oxygen radical absorbance capacity (ORAC). The highest ARs content (μg/g) was found in cultivars Emmit (1522), Harvard (1305), Warthog (1170), and Superior (853), grown in Ridgetown. The relative saturated and unsaturated ARs (%) were 89 and 11, respectively. Total ARs content, their composition, TPC and antioxidant activity of wheat bran extracts were significantly (P < 0.05) affected by location and cultivar and their interaction. TPC, %DPPH_dis, and ORAC values for different wheat bran sample extracts ranged from 3 to 58 (mg FAE/g), 5 to 68 (%), and 6 to 94 (μmol TE/g), respectively. Our work provides a detailed examination of region and cultivar effects on potential of ARs in wheat bran and the results can be used for screening and breeding purposes.     

Effects of genotype,harvest year and genotype-by-harvest year interactions on arabinoxylan,endoxylanase activity and endoxylanase inhibitor levels in wheat kernels

The effects of genotype, harvest year and their interaction on the levels of arabinoxylans (AX), endoxylanases and endoxylanase inhibitors in wheat were studied using 14 varieties grown in three successive growing periods with diverse climatological conditions. Relations with more commonly evaluated wheat characteristics such as yield, thousand kernel weight, specific weight, protein level, Hagberg falling number (HFN) and α-amylase activity level were examined. Water extractable arabinoxylan (WE-AX) levels in wheat varied much more than total arabinoxylan (TOT-AX) levels. This variability was mainly genetically determined, but harvest year also had an important effect. Total endoxylanase activity levels varied more than a factor of 20 between the different wheat samples. Endogenous endoxylanases typically accounted for only 10–15% of this activity, while wheat-associated microbial endoxylanases accounted for the remaining 85–90%. However, when preharvest sprouting occurred, the contribution of endogenous endoxylanases could sometimes amount to over 40% of this total activity. Endogenous endoxylanase activity levels were mainly determined by the interaction of genotype and harvest year, while wheat-associated microbial endoxylanase activity levels were predominantly determined by genotype alone. Endogenous and microbial endoxylanase activity levels were strongly correlated, suggesting that wheat varieties which are susceptible to preharvest sprouting are often also susceptible to microbial contamination. The TAXI and XIP-type endoxylanase inhibitor levels varied by a factor of 8 and 1.8, respectively. They were mainly determined by genotype and were rather similar in the different growing periods.     

Effects of fungicide treatment,N-fertilisation and harvest date on arabinoxylan,endoxylanase activity and endoxylanase inhibitor levels in wheat kernels

Fungicide treatment had a significant impact on endoxylanase activity and XIP levels, but did not affect arabinoxylan (AX) and TAXI levels. The different response of TAXI and XIP type inhibitors to fungicide treatment is interesting. N-fertilisation did not affect AX levels, but significantly increased TAXI and XIP type inhibitor levels. Wheat-associated microbial endoxylanase activity levels were also affected by nitrogen supply, but levels of the endogenous enzyme did not change, except when sprouting occurred. The weather conditions before harvest had no influence on total AX (TOT-AX) and inhibitor levels, but had a large impact on both microbial and endogenous endoxylanase activity and water extractable AX (WE-AX) levels. Under most conditions, endoxylanase activity levels were related to those of α-amylases, liquefaction numbers (LN) and specific weights. WE-AX levels were often weakly but significantly correlated with endoxylanase activity levels, indicating that it is possible that part of the WE-AX in wheat originates from AX degradation by endoxylanases in the field. These results clearly indicate that agronomic circumstances significantly affect the levels of AX, endoxylanases and their inhibitors in wheat, and consequently could affect wheat quality.     

Applications of pre-emergent pyroxasulfone,flufenacet and their mixtures with triallate for the control of Bromus diandrus (ripgut brome) in no-till wheat (Triticum aestivum) crops of southern Australia

Four field experiments were conducted over a three-year period in Victoria and South Australia to investigate the effectiveness of pre-emergence (PRE) applications of pyroxasulfone, flufenacet and their mixtures with triallate for the control of Bromus diandrus in spring wheat. Herbicide mixtures of pyroxasulfone plus triallate and flufenacet plus triallate applied PRE to wheat provided consistently high levels of B. diandrus control (≥85%). In contrast, applications of pyroxasulfone and flufenacet applied alone along with trifluralin plus metribuzin (a common farmer practice in southern Australia) provided more variable control of B. diandrus (33–90%). Pyroxasulfone plus triallate treatments had a much lower (≤47 panicles m⁻²) panicle density of B. diandrus than trifluralin plus metribuzin (42–318 panicles m⁻²) and the non-treated control (118–655 panicles m⁻²). PRE herbicides which were safe to spring wheat and provided the greatest level of control of B. diandrus resulted in significantly (P < 0.05) higher grain yields at Culgoa (120%) and Gama (13%) than non-treated wheat (720 and 1740 kg ha⁻¹). Although flufenacet was effective against B. diandrus, crop phytotoxicity at the higher dose (900 g ai ha⁻¹) reduced spring wheat grain yield. Based on these results, PRE pyroxasulfone plus triallate could play an important role in the management of B. diandrus in spring wheat. However, high cost of these herbicides (AUS$35-$70 ha⁻¹) may limit their adoption in low rainfall and low yielding wheat environments in southern Australia where B. diandrus is most prevalent.