Phytate negatively influences wheat dough and bread characteristics by interfering with cross-linking of glutenin molecules

The influence of added phytate on dough properties and bread baking quality was studied to determine the role of phytate in the impaired functional properties of whole grain wheat flour for baking bread. Phytate addition to refined flour at a 1% level substantially increased mixograph mixing time, generally increased mixograph water absorption, and reduced the SDS-unextractable protein content of dough before and after fermentation as well as the loaf volume of bread. The added phytate also shifted unextractable glutenins toward a lower molecular weight form and increased the iron-chelating activity of dough. It appears that phytate negatively affects gluten development and loaf volume by chelating iron and/or binding glutenins, and consequently interfering with the oxidative cross-linking of glutenin molecules during dough mixing. Phytate could be at least partially responsible for the weak gluten network and decreased loaf volume of whole wheat flour bread as compared to refined flour bread.     

Introgression of a major gene for high grain protein content in some Indian bread wheat cultivars

In bread wheat, high grain protein content (GPC) determines nutritional value, processing properties and quality of the end-product. In view of this, marker-assisted selection (MAS) was performed for introgression of a major gene for high GPC (Gpc-B1) into 10 wheat genotypes. As a result, 124 BC₃F₅/F₆ progenies with Gpc-B1 were developed and evaluated in multi-location field trials. Significant interaction of Gpc-B1 with the recipient parent genotypes and the environment was noticed. However, a total of seven MAS-derived progenies with significantly higher GPC (14.83-17.85%) than their recipient parental genotypes and having no yield penalty were obtained. In these selected progenies, no significant negative correlation of grain yield with GPC (%) or protein yield was observed suggesting that GPC could be improved without yield penalty. This study thus suggested that MAS in combination with phenotypic selection is a useful strategy for development of wheat genotypes with high GPC associated with no loss in yield.     

Phytase activity, phytate, iron, and zinc contents in wheat pearling fractions and their variation across production locations

Pearling is an effective method for evaluating the distribution of chemical components in wheat grain. Twelve pearling fractions (P₁–P₁₂) of wheat grain were obtained using two rice polishers for 10 cultivars (six soft red wheats and four hard white wheats) grown at two locations with different environmental conditions in Jiangsu Province, China. The results show that the effects of cultivar, location, and pearling on wheat flour phytase activity, phytate, iron, and zinc contents were all significant, with pearling having the greatest effect. All the four components showed a diminishing trend as pearling progressed from the outer layers to the inner part of wheat grain. Generally, the P₂ fraction (the outer 4–8% layer of wheat grain) had the highest phytase activity and phytate and iron contents, whereas the P₁ fraction (the outer 0–4% layer) ranked the highest for zinc content. Growing location had a large influence on grain phytase, phytate, and iron, but the differences between locations decreased as pearling level increased.     

Definition of the low molecular weight glutenin subunit gene family members in a set of standard bread wheat (Triticum aestivum L.) varieties

Low-molecular-weight glutenin subunits (LMW-GS) are a class of seed storage proteins that play a major role in the determination of the viscoelastic properties of wheat dough. The LMW-GSs are encoded by multi-gene families at the Glu-A3, Glu-B3 and Glu-D3 loci, with more than 15 genes present in most bread wheat varieties. However, the genic profile associated with different alleles has not been clearly defined. Here, the LMW-GSs in a set of standard varieties were analyzed using molecular markers. In most cases, each Glu-3 allele was represented by a specific haplotype; however, some alleles were undistinguishable. The Glu-A3e and Glu-A3g alleles showed an identical marker haplotype, as did the alleles Glu-B3c and Glu-B3d, and Glu-B3f and Glu-B3ab. In contrast, two haplotypes among varieties designated Glu-D3c were differentiated. The marker profiles present at the Glu-D3 locus exhibited less variation compared to the genes at the Glu-A3 and Glu-B3 loci. Results show the potential of the LMW-GS gene marker system in the characterization of the LMW-GS alleles present in specific bread wheat varieties, and its reconciliation with protein-based nomenclature. This approach will advance the understanding of the contribution of each of the LMW-GS gene alleles in the control of the end-use quality.     

Grain cadmium and zinc concentrations in wheat as affected by genotypic variation and potassium chloride fertilization

Thirteen bread wheat (Triticum aestivum L.) and two durum wheat (Triticum turgidum L. var. durum) cultivars were grown over six site-years to identify differences in grain Cd and Zn concentrations, as affected by genotypic variation and soil application of potassium chloride (KCl) fertilizer. Application of KCl fertilizer did not consistently affect grain Cd concentration of wheat cultivars, but increased average grain yield and decreased average grain Zn in 4 of 6 site-years. However, soil type and year had significant effects on grain Cd and Zn, indicating a strong environmental effect on grain quality. Grain concentrations of Cd and Zn were generally lower for the clay loam (CL) than the fine sandy loam (FSL) soils. The wheat cultivars showed significant genotypic differences in grain concentrations of Cd and Zn, suggesting the potential of breeding to reduce Cd and increase Zn concentrations in grain. The two durum cultivars contained high concentrations of Cd but not Zn compared to the bread wheat. The interaction between cultivars and site-years was significant for grain Zn, but not for grain Cd, suggesting that grain Cd is a more stable trait than grain Zn across environments. Grain Zn and Cd were not related to each other but they both correlated negatively with grain yield. The lack of relationship between Zn and Cd suggests that breeding for enhanced Zn concentration can be attained without necessarily affecting grain Cd concentration. The negative relationship between Cd and Zn concentration and dry matter yield was likely the result of biological dilution, suggesting that genetic improvement leading to increased yield may concurrently decrease mineral concentration. Results of this study are useful to improve the mineral composition of wheat used for human consumption through the development of cultivars and use of agronomic management practices that increase Zn and/or reduce Cd concentrations in wheat grain.     

Volume, texture, and molecular mechanism behind the collapse of bread made with different levels of hard waxy wheat flours

Physico-chemical properties of bread baked by partially replacing normal wheat (Triticum aestivum L.) flour (15, 30, and 45%) with two hard waxy wheat flours were investigated. Substitution with waxy wheat flour resulted in higher loaf volume and softer loaves. However, substitution at >30% resulted in excessive post-bake shrinkage and a ‘key-hole’ shape with an open crumb structure. Bread crumb microstructure indicated a loss of starch granule rigidity and fusing of starch granules. The cells in the interior of the bread did not become gas-continuous and as a result, shrunk as the loaf cooled. Soluble starch content was significantly higher in bread crumb containing waxy wheat flour than in control bread. Debranching studies indicated that the soluble starch in bread made with 30-45% hard waxy wheat flour was mostly amylopectin. Incorporation of waxy wheat flour resulted in softer bread immediately after baking but did not retard staling upon storage.     

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.     

Properties of whole grain wheat flour and performance in bakery products as a function of particle size

The aim of this study was to evaluate the effect of particle size distribution on composition, properties rheological, pasting, microstructural and baking properties of whole grain wheat flour (WGWF) of three different particles sizes (194.9 μm, 609.4 μm and 830.0 μm). The quantification of free sulfhydryl groups (-SH) of WGWF samples, together with the effects observed in the behavior of the dough and bread showed that particle size influences the functionality of the gluten network in a differentiated way. Firmer and lower breads volume compared to refined wheat flour (RF) were correlated with the quality of the gluten network. In the sample of finer particles, more pronounced adverse effects in quality (dough rheology, bread volume and texture) compared to the medium and coarse particle size sample suggests that the larger contact surface and the increased release of reactive compounds due to cell rupture interact with the gluten-forming proteins changing their functionality.     

CIMMYT-selected derived synthetic bread wheats for rainfed environments: Yield evaluation in Mexico and Australia

Synthetic backcrossed-derived bread wheats (SBWs) from CIMMYT were grown in the Northwest of Mexico at Centro de Investigaciones Agrícolas del Noroeste (CIANO) and sites across Australia during three seasons. During three consecutive years Australia received “shipments” of different SBWs from CIMMYT for evaluation. A different set of lines was evaluated each season, as new materials became available from the CIMMYT crop enhancement program. These consisted of approximately 100 advanced lines (F7) per year. SBWs had been top and backcrossed to CIMMYT cultivars in the first two shipments and to Australian wheat cultivars in the third one. At CIANO, the SBWs were trialled under receding soil moisture conditions. We evaluated both the performance of each line across all environments and the genotype-by-environment interaction using an analysis that fits a multiplicative mixed model, adjusted for spatial field trends. Data were organised in three groups of multienvironment trials (MET) containing germplasm from shipment 1 (METShip1), 2 (METShip2), and 3 (METShip3), respectively. Large components of variance for the genotype × environment interaction were found for each MET analysis, due to the diversity of environments included and the limited replication over years (only in METShip2, lines were tested over 2 years). The average percentage of genetic variance explained by the factor analytic models with two factors was 50.3% for METShip1, 46.7% for METShip2, and 48.7% for METShip3. Yield comparison focused only on lines that were present in all locations within a METShip, or “core” SBWs. A number of core SBWs, crossed to both Australian and CIMMYT backgrounds, outperformed the local benchmark checks at sites from the northern end of the Australian wheat belt, with reduced success at more southern locations. In general, lines that succeeded in the north were different from those in the south. The moderate positive genetic correlation between CIANO and locations in the northern wheat growing region likely reflects similarities in average temperature during flowering, high evaporative demand, and a short flowering interval. We are currently studying attributes of this germplasm that may contribute to adaptation, with the aim of improving the selection process in both Mexico and Australia.     

Molecular characterization of Glu-B3 locus in wheat cultivars and segregating populations

Bread wheat quality constitutes a key trait for the demands of the baking industry as well as the broad consumer preferences. The role of the low molecular weight glutenin subunits (LMW-GS) with regard to bread quality is so far not well understood owing to their genetic complexity and to the use of different nomenclatures and standards for the LMW-GS assignment by different research groups, which has made difficult the undertaking of association studies between genotypes and bread quality. The development of molecular markers to carry out genetic characterization and allele determination is demanding. Nowadays, the most promising LMW gene marker system is based on PCR and high resolution capillary electrophoresis for the simultaneous analysis of the complete multigene family. The molecular analysis of the bread wheat Glu-B3 locus in F₂ and F_4:6 populations expressed the expected one-locus Mendelian segregation pattern, thus validating the suitability of this marker system for the characterization of LMW-GS genes in segregating populations, allowing for the successful undertaking of studies related to bread-making quality. Moreover, the Glu-B3 allele characterization of standard cultivars with the molecular marker system has revealed its potential as a complementary tool for the allelic determination of this complex multigene family.     

Investigation and genome-wide association study of grain copper content in Chinese common wheat

Copper is a necessary trace mineral for the human body, and its deficiency threatens human health. Here, a panel of 243 Chinese wheat cultivars from five replications was used to measure the grain copper content (GCC) by atomic absorption spectrometry. Phenotypic analysis results revealed that the averaged GCC of surveyed cultivars ranged from 6.81 to 11.36 mg/kg with an average of 9.23 mg/kg. A genome-wide association study (GWAS) indicated that a total of 489 single-nucleotide polymorphisms (SNPs) were significant, explaining 10.1%–32.6% of the phenotypic variation and were mainly distributed on chromosomes 2A and 5A. Further analysis indicated that GCC_Hap_2A1, GCC_Hap_3B1, and GCC_Hap_5A1 may be important genetic loci that regulate GCC in wheat. Linkage mapping using a bi-parental population detected four QTLs on 1D, 6A, 6B, and 7D, explaining 8.66%, 7.55%, 8.21%, and 4.71% of the phenotypic variation, respectively. Additionally, two of the significant SNPs were located on 1D, as detected by GWAS, and were within the interval of QGCC.hau-1D, suggesting that this locus plays an important role in regulating wheat GCC. This study dissected the genetic mechanism of GCC in wheat and provides useful information for the utilization of high-GCC wheat germplasm by marker-assisted selection in wheat quality breeding.     

Silencing of puroindoline a alters the kernel texture in transgenic bread wheat

Grain hardness is an important end-use quality parameter of bread wheat, and one of the most important characters for quality improvement. The objective of this study was to further understand the function of puroindolines and the underlying mechanism in the formation of kernel texture. The highly efficient expression vector pUBPa harboring puroindoline a (Pina) was introduced into the bread wheat cultivar Zhongyou 9507-60 via biolistic transformation and transgenic plants were obtained. The integration of the foreign Pina gene was confirmed by PCR and genomic DNA Southern blot analysis. The levels of friabilin on the surface of water-washed starch granules varied among the transgenic lines. SDS-PAGE analysis of Triton X-114 extracted protein showed that the PINA protein was absent in three transgenic lines, indicating that the endogenous Pina gene most likely had been co-suppressed by the over-expression of the Pina transgene. SKCS kernel hardness and scanning electron microscopy analysis further confirmed the changes of kernel texture in these lines.     

Grain and milling characteristics and their relationship with selected mixogram parameters in hard red bread wheat

Breeders in South Africa are faced with the problem that quality testing is only done in advanced phases of the bread wheat breeding programme when enough seed is available. This means that lines not meeting quality requirements of the South African industry for cultivar release are only discarded during the advanced breeding phases. The aim of this study was to determine relationships between grain and milling characteristics and mixogram parameters and to determine whether these characteristics can be used for selection of acceptable mixogram parameters and vice versa. A mixograph with Mixsmart software was used to analyse 10 bread wheat cultivars, in four replications at three different locations. Thirteen mixogram parameters were used to determine correlations with important grain and milling characteristics. Highly significant correlations were observed between mixogram parameters and grain as well as milling characteristics, although not with hectolitre mass, thousand kernel mass, vitreous kernels, falling number or flour colour. Multiple coefficient of determination was low to moderate for grain characteristics and low for milling characteristics as independent variables in explaining the variation in several mixogram parameters. In spite of the highly significant correlations, grain and milling characteristics explained little of the variation in mixogram parameters in this study.     

Use of a global wheat core collection for association analysis of flour and dough quality traits

Flour and dough quality are very important breeding traits for wheat (Triticum aestivum L.) the selection of which would benefit from linked molecular markers. Association analysis allows the identification of genes or quantitative trait loci (QTL) related to target traits. The effectiveness of this approach depends on the availability of a densely genotyped population with large genetic variability for the traits of interest. Our objective was to identify chromosomal regions associated with flour and dough quality traits using a core collection built by maximizing the genetic diversity and phenotypic variability. We investigated the association of DArT, SSR and SNP markers with grain protein content, grain hardness, water-extractable arabinoxylan (WEAX) viscosity, wholemeal flour color and dough rheology.Out of 803 markers tested, 130 markers spread over the genome were associated with at least one trait, varying from 20 associated with WEAX viscosity to 60 associated with dough quality. Most chromosome regions known to determine wheat quality from the study of several bi-parental recombinant inbred lines were confirmed here and some new regions were identified. Associations were found for each trait studied, demonstrating that the core collection is a useful tool for QTL association mapping of these and other traits of interest.     

Influence of phenolic acid content on sensory perception of bread and crackers made from red or white wheat

Despite the health benefits of wholegrain, consumer acceptance of wholegrain products remains an issue due to the presence of characteristic flavours that some consumers consider to be unacceptable. It was hypothesized that phenolic acids could be contributing to the perceived unacceptable flavours described in wholegrain products. The purpose of this study was to examine the relationship between total phenolic acid content (TPAC) and phenolic acids as quantified by HPLC, to the sensory properties of wholegrain products using partial least squares (PLS) mapping. Red and white wheat flours were investigated in an intermediate (bread) and low (cracker) moisture product system. Red and white wheat demonstrated different phenolic acid profiles despite having similar TPAC. Within the bread crumb, the free and bound phenolic acids provided the best predictive scores; whereas only bound phenolic acids provided high predictive scores in crackers. This suggests that the contribution of phenolic acids to flavour characteristics of wholegrain products varies depending upon the product moisture.     

Effects of a late N fertiliser dose on storage protein composition and bread volume of two wheat varieties differing in quality

Wheat is an important source of energy and protein for humans all over the world and is mainly consumed in form of baked goods, for which a high baking quality is required. The main parameter for bread-making quality predictions of wheat flours is the grain protein concentration (GPC). Therefore, the GPC determines the value of the harvested wheat. Unfortunately, the GPC appears to be no longer an appropriate parameter for baking quality evaluation, given that, especially for high protein varieties, the correlation between GPC and bread volume is poor. A late N application is commonly used to increase GPC and enhance the bread-making quality of wheat flours. To minimise the environmental problems involved in the late use of N fertilisers, it is important to know how much N is necessary to achieve the desired effects. Therefore, in this study, the effects of two different doses of late N application on the GPC, as well as storage protein composition and bread volume were tested in two wheat varieties from different quality groups under field conditions in Germany. The findings of this experiment demonstrate that a low late N application appears to be sufficient to achieve a good baking quality of wheat flours. These results confirm the presumption that GPC is not a suitable parameter for bread-making quality predictions. As the relationships between the single storage protein fractions and bread volume were poor, it can be concluded that only the combined alterations within all gluten protein fractions explain the rise in bread volume.     

Effect of high-nitrogen fertilizer on gliadin and glutenin subproteomes during kernel development in wheat(Triticum aestivum L.)

Nitrogen(N),a macronutrient essential for plant growth and development,is needed for biosynthesis of protein and starch,which affect grain yield and quality.Application of high-N fertilizer increases plant growth,grain yield,and flour quality.In this study,we performed the first comparative analysis of gliadin and glutenin subproteomes during kernel development in the elite Chinese wheat cultivar Zhongmai 175 under high-N conditions by reversed-phase ultra-performance liquid chromatography and twodimensional difference gel electrophoresis(2D-DIGE).Application of high-N fertilizer led to significant increases in gluten macropolymer content,total gliadin and glutenin content,and the accumulation of individual storage protein components.Of 126 differentially accumulated proteins(DAPs)induced by high-N conditions,24 gliadins,12 high-molecularweight glutenins,and 27 low-molecular-weight glutenins were significantly upregulated.DAPs during five kernel developmental stages displayed multiple patterns of accumulation.In particular,gliadins and glutenins showed respectively five and six accumulation patterns.The accumulation of storage proteins under high-N conditions may lead to improved dough properties and bread quality.     

Influence of wheat variety and dough preparation on FODMAP content in yeast-leavened wheat breads

FODMAPs are fermentable oligo-, di, and monosaccharides and polyols, which can have adverse effects on human health. Especially in individuals with gastrointestinal disorders such as irritable bowel syndrome, ingestion of FODMAPs may trigger or aggravate symptoms like abdominal pain, bloating, or diarrhea. Our objectives were to investigate the FODMAP content in the flour of 21 wheat varieties and in their 42 yeast-leavened breads prepared with a short (110 min) or a long dough fermentation (24 h), the latter according to a typical baker's recipe. Fructan, glucose, fructose and excess fructose were measured using enzymatic kits. On average, the breads of both dough fermentations had a FODMAP content reduced by > 65% compared to that of the whole grain wheat flour. Average FODMAP content of both dough fermentations was 0.22 g per 100 g fresh bread. FODMAP content tended to be lower in the long compared to the short dough fermentation, however, the difference was not statistically significant. We also found that the 21 wheat varieties differed up to five times in their potential to form FODMAPs in bread. In conclusion, the choice of a low fructan wheat variety coupled with long dough fermentation with sourdough and yeast is best to minimize FODMAPs in breads.     

Association of Puroindoline b-B2 variants with grain traits,yield components and flag leaf size in bread wheat (Triticum aestivum L.) varieties of the Yellow and Huai Valleys of China

A total of 169 wheat (Triticum aestivum L.) varieties (landraces and cultivars) were used to asses the relationship between Puroindoline D1 alleles and Puroindoline b-B2 variants and grain hardness, other grain traits, yield components, and flag leaf size. Results indicated that the average SKCS hardness of Pinb-B2v3 varieties was significantly greater than that of Pinb-B2v2 varieties within the soft Puroindoline D1 haplotype sub-group. Conversely, no statistically significant difference was obtained for SKCS hardness between varieties with the Pinb-B2v3 vs. Pinb-B2v2 alleles within the two hard Puroindoline D1 haplotypes (Pinb-D1b and Pinb-D1p sub-groups). Therefore, the Puroindoline b-B2 gene may have a bigger impact on soft wheat varieties than hard. Across all varieties, thousand-kernel weight, grain weight per spike, grain diameter, grain number per spike, flag leaf width and area of Pinb-B2v3 varieties were significantly greater than those possessing Pinb-B2v2. These results indicated that the Pinb-B2v3 allele was associated with preferable grain yield traits compared to the Pinb-B2v2 allele in bread wheat. This study provides evocative information for better understanding the molecular and genetic basis of wheat grain yield.     

Effects of allelic variation of HMW-GS and LMW-GS on mixograph properties and Chinese noodle and steamed bread qualities in a set of Aroona near-isogenic wheat lines

High-molecular-weight glutenin (HMW-GS) and low-molecular-weight glutenin (LMW-GS) subunits play an important role in determining wheat quality. To clarify the contribution of each subunit/allele to processing quality, 25 near-isogenic lines with different HMW-GS and LMW-GS compositions grown at two locations during the 2010 cropping season were used to investigate the effects of allelic variation on milling parameters, mixograph properties, raw white Chinese noodle (RWCN) and northern style Chinese steamed bread (NSCSB) qualities. The results showed that Glu-B1 and Glu-B3 made a large contribution to determining mixograph properties and processing quality, respectively. Subunit pairs 17 + 18 and 5 + 10, and alleles Glu-A3b, Glu-A3d, Glu-B3g and Glu-D3f made significant contributions to mixograph properties and no significant difference was detected on most parameters of RWCN and NSCSB for the allelic variation of HMW-GS and LMW-GS. The allelic interactions among glutenin loci had significant effects on wheat quality. The line with 1, 17 + 18, 2 + 12, Glu-A3c, Glu-B3b, Glu-D3c associated with superior mixograph properties, the line with 1, 7 + 9, 2 + 12, Glu-A3c, Glu-B3d, Glu-D3c had superior viscoelasticity of RWCN, and the line with 1, 7 + 9, 2 + 12, Glu-A3e, Glu-B3b, Glu-D3c had the highest total score of NSCSB. These results provide useful information for genetic improvement of the qualities of traditional Chinese wheat products.