Influence of Low Molecular Weight Glutenins on Viscoelastic Properties of Intact Wheat Kernels and Their Relation to Functional Properties of Wheat Dough

The mechanical and viscoelastic properties of intact wheat kernels of 36 wheat cultivars differing in low molecular weight glutenin subunit (LMW‐GS) composition (loci Glu‐A3, Glu‐B3, and Glu‐D3) were evaluated using load‐compression tests. Comparison among genotypic groups representing Glu‐3 allelic variants showed that groups representing the alleles Glu‐A3 b, c, and d; Glu‐B3 d, g, and h; and Glu‐D3 a, b, and d, had harder kernel texture, higher kernel elastic work and larger gluten strength‐related parameters than those possessing alleles Glu‐A3 e; Glu‐B3 f, i and j (translocation 1B/1R); and Glu‐D3 d. Modulus of elasticity (stress to strain ratio) showed low values (111.9–168.8 MPa) for allelic groups possessing poor elastic properties (Glu‐A3 e; Glu‐B3 f, i, and j; and Glu‐D3 d), and high values (179.8–222.6 MPa) for allelic groups possessing high kernel elastic properties (Glu‐A3 b c, and d; Glu‐B3 d, g, and h; and Glu‐D3 a, b and c). The highest values for gluten strength‐related parameters (SDS‐sedimentation, dough mixing time, and dough strength [W]) corresponded to allelic groups Glu‐A3 d; Glu‐B3 d and g; and Glu‐D3 d, while the lowest corresponded to Glu‐A3 e and Glu‐B3 j. No significant differences were observed among groups with regard to gluten extensibility parameters; however, the highest P/L value (least extensibility) corresponded to Glu‐B3 j, which indicates presence of 1B/1R translocation. Except for the Glu‐B3 j (translocation 1B/1R) allele, which presented more variation within samples, a general relationship between kernel viscoelastic properties and dough viscoelastic properties was observed; samples showing higher elastic work to plastic work ratio (E/P) tended to possess better gluten strength than cultivars with low E/P ratio.     

Synergistic and Additive Effects of Three High Molecular Weight Glutenin Subunit Loci. I. Effects on Wheat Dough Rheology

The high molecular weight glutenin subunits (HMW‐GS) play an important role in governing the functional properties of wheat dough. To understand the role of HMW‐GS in defining the basic and applied rheological parameters and end‐use quality of wheat dough, it is essential to conduct a systematic study where the effect of different HMW‐GS are determined. This study focuses on the effect of HMW‐GS on basic rheological properties. Eight wheat lines derived from cvs. Olympic and Gabo were used in this study. One line contained HMW‐GS coded by all three loci, three lines were each null at one of the loci, three lines were null at two of the loci and one line null at all three loci. The flour protein level of all samples was adjusted to a constant 9% by adding starch. In another set of experiments, in addition to the flour protein content being held at 9%, the glutenin‐to‐gliadin ratio was maintained at 0.62 by adding gliadin. Rheological properties such as elongational, dynamic, and shear viscometric properties were determined. The presence of Glu‐D1 subunits (5+10) made a significantly larger contribution to dough properties than those encoded by Glu‐B1 (17+18), while subunit 1, encoded by Glu‐A1, made the least contribution to functionality. Results also confirmed that HMW‐GS contributed to strength and stability of dough.     

Synergistic and Additive Effects of Three High Molecular Weight Glutenin Subunit Loci. II. Effects on Wheat Dough Functionality and End‐Use Quality

Understanding the relationship between basic and applied rheological parameters and the contribution of wheat flour protein content and composition in defining these parameters requires information on the roles of individual flour protein components. The high molecular weight glutenin subunit (HMW‐GS) proteins are major contributors to dough strength and stability. This study focused on eight homozygous wheat lines derived from the bread wheat cvs. Olympic and Gabo with systematic deletions at each of three HMW‐GS encoding gene loci, Glu‐A1, Glu‐B1, and Glu‐D1. Flour protein levels were adjusted to a constant 9% by adding starch. Functionality of the flours was characterized by small‐scale methods (2‐g mixograph, microextension tester). End‐use quality was evaluated by 2‐g microbaking and 10‐g noodle‐making procedures. In this sample set, the Glu‐D1 HMW‐GS (5+10) made a significantly larger contribution to dough properties than HMW‐GS coded by Glu‐B1 (17+18), while subunit 1 coded by Glu‐A1 made the smallest contribution to functionality. These differences remained after removing variations in glutenin‐to‐gliadin ratio. Correlations showed that both basic rheological characteristics and protein size distributions of these flours were good predictors of several applied rheological and end‐use quality tests.     

Composition of HMW and LMW Glutenin Subunits and Their Effects on Dough Properties,Pan Bread,and Noodle Quality of Chinese Bread Wheats

Knowledge of composition of high molecular weight glutenin subunits (HMW‐GS) and low molecular weight glutenin subunits (LMW‐GS) and their associations with pan bread and noodle quality will contribute to genetically improving processing quality of Chinese bread wheats. Two trials including a total of 158 winter and facultative cultivars and advanced lines were conducted to detect the allelic variation at Glu‐1 and Glu‐3 loci by SDS‐PAGE electrophoresis and to understand their effects on dough properties, pan bread, and dry white Chinese noodle (DWCN) quality. Results indicate that subunits/alleles 1 and null at Glu‐A1, 7+8 and 7+9 at Glu‐B1, 2+12 and 5+10 at Glu‐D1, alleles a and d at Glu‐A3, and alleles j and d at Glu‐B3 predominate in Chinese germplasm, and that 34.9% of the tested genotypes carry the 1B/1R translocation (allelic variation at Glu‐D3 was not determined because no significant effects were reported previously). Both variations at HMW‐GS and LMW‐GS/alleles and loci interactions contribute to dough properties and processing quality. For dough strength related traits such as farinograph stability and extensigraph maximum resistance and loaf volume, subunits/alleles 1, 7+8, 5+10, and Glu‐A3d are significantly better than those of their counterpart allelic variation, however, no significant difference was observed for the effects of d, b, and f at Glu‐B3 on these traits. For extensigraph extensibility, only subunits 1 and 7+8 are significantly better than their counterpart alleles, and alleles d and b at Glu‐B3 are slightly better than others. For DWCN quality, no significant difference is observed for HMW‐GS at Glu‐1, and Glu‐A3d and Glu‐B3d are slightly better than other alleles. Glu‐B3j, associated the 1B/1R translocation, has a strong negative effect on all quality traits except protein content. It is recommended that selection for subunits/alleles 1, 7+8, 5+10, and Glu‐A3d could contribute to improving gluten quality and pan bread quality. Reducing the frequency of the 1B/1R translocation will be crucial to wheat quality improvement in China.     

Breadmaking Quality of Selected Durum Wheat Genotypes and Its Relationship with High Molecular Weight Glutenin Subunits Allelic Variation and Gluten Protein Polymeric Composition

Twenty‐seven durum wheat genotypes originating from different geographical areas, all expressing LMW‐2 at Glu‐B3, and five bread wheats were evaluated for flour mixing properties, dough physical characteristics, and baking performance. Gluten polymeric composition was studied using size‐exclusion HPLC of unreduced flour protein extracts. As a group, durum wheats had poorer baking quality than bread wheats in spite of higher protein and total polymer concentrations. Durum wheats exhibited weaker gluten characteristics, which could generally be attributed to a reduced proportion of SDS‐unextractable polymer, and produced less extensible doughs than did bread wheats. However, substantial variation in breadmaking quality attributes was observed among durum genotypes. Better baking performance was generally associated with greater dough extensibility and protein content, but not with gluten strength related parameters. Extensibility did not correlate with gluten strength or SEHPLC parameters. Genotypes expressing high molecular weight glutenin subunits (HMW‐GS) 6+8 exhibited better overall breadmaking quality compared with those expressing HMW‐GS 7+8 or 20. Whereas differences between genotypes expressing HMW‐GS 6+8 and those carrying HMW‐GS 7+8 could only be attributed to variations in extensibility, the generally inferior baking performance of the HMW‐GS 20 group relative to the HMW‐GS 6+8 group could be attributed to both weaker and less extensible gluten characteristics.     

Protein and Quality Characterization of Triticale Translocation Lines in Breadmaking

Introduction of high molecular weight glutenin subunits (HMW‐GS) from the Glu‐D1d locus of wheat into triticale restores the genetic constitution of high molecular weight glutenin loci to that of wheat and subsequently improves the breadmaking quality of triticale. One means of achieving such restoration of the genetic constitution is through the use of translocation lines. The aim of this study was to evaluate and compare the performance of translocations 1A.1D and 1R.1D with HMW‐GS 5+10 and 2+12 in terms of physical dough tests and baking quality using four different sets of triticale lines, GDS7, Trim, Rhino, and Rigel. In general, significantly lower milling quality (flour yield), very low mixing times with lower loaf volume were typical of all the triticales studied except 1A.1D 5+10 lines, when compared to hard wheat flour (Pegaso). Among the lines studied, significantly higher loaf volume, mixograph dough development time (MDDT), and maximum resistance to extension (R_max) were observed with 1A.1D 5+10 lines indicating that translocation of the Glu‐D1d allele with HMW‐GS 5+10 was beneficial in terms of improving the quality attributes. Although pure triticale flour from these lines did not possess the functional characteristics for good quality bread, the translocation 1A.1D that contains HMW glutenin subunits 5+10 showed significant improvement in quality characteristics, and could reasonably be expected to yield commercially satisfactory bread loaves when combined with bread wheat flour. Significantly higher UPP, R_max, and MDDT values along with a lower gliadin‐to‐glutenin ratio in 1A.1D 5+10 of GDS7 and Rigel sets indicate that the molecular weight distribution was shifted to higher molecular weights, resulting in greater dough strength associated with 5+10 subunits.     

A Novel Pair of HMW Glutenin Subunits from Aegilops searsii Improves Quality of Hexaploid Wheat

This study involved screening of wild species of wheat in search of functionally useful seed storage proteins for improvement of breadmaking quality of wheat (Triticum aestivum). After screening of 177 disomic addition lines (DALs) of wheat belonging to different wild species, Aegilops searsii DALs were selected and studied in detail. These DALs of Ae. searsii were from chromosome 1S^s to 7S^s in the background of cultivated wheat cv. Chinese Spring (CS). By analyzing these addition lines, genetic loci of actively expressed genes for the high molecular weight glutenin subunits (HMW‐GS) and gliadin were found on the chromosome 1S^s for the first time and have been designated as Glu‐S^s1 and Gli‐S^s1, respectively. Disomic addition line of chromosome 1S^s (DAL1S^s) showed improved dough strength in different generations compared with CS. SDS sedimentation value and specific sedimentation of DAL1S^s were higher than CS. Mixograph peak height and band width were higher, with no difference in mixing peak time from CS. All these factors indicate a positive effect of quantity as well as quality of gluten proteins of Ae. searsii. This was further supported by increased polymer formation in DAL1S^s because the ratio of unextractable polymeric protein to total polymeric protein (UPP/TPP%) of DAL1S^s was significantly higher than CS. Genes for HMW‐GS (major determinant of end‐product quality in wheat) of Ae. searsii were cloned and sequenced from the DAL1S^s. Phylogenetic analysis of deduced amino acid sequences showed that both x and y HMW‐GS were more similar to that of D genome rather than B genome of wheat. Although S genome is structurally more similar to B genome of wheat, functionally it is more similar to the D genome of wheat and possesses good quality HMW‐GS required for improvement of breadmaking quality of wheat.     

Mixtures of Two Argentinean Wheat Cultivars of Different Quality: A Study on Breadmaking Performance

Commercial Argentinean wheat flours are commonly composed of at least two wheat cultivars to obtain products of constant quality. Flours from two different wheats (Buck Pronto [BP] and Klein Escudo [KE]) with different protein profiles and breadmaking performance were assayed. Glu‐1 alleles are expressed in BP with 2, 7+8, 5+10 HMW glutenins subunits, while in KE 2, 7+9, 5+10 HMW glutenins subunits are present. Different sample blends (BP and KE) of 100:0, 75:25, 50:50, 25:75, and 0:100 were analyzed to relate composition of blends to the characteristics of dough and breads obtained from them. Physicochemical assays, alveograms, farinograms, and the SDS sedimentation test (SDSS test) were applied to characterize pure flours and blends. Rheological behavior of dough was studied by texture profile analysis (TPA) and dynamic assays. Scanning electron microscopy (SEM) was used to analyze dough microstructure. Alveographic W and farinographic stability values of blends with ≤50% KE were higher than expected. The same behavior was observed in SDSS‐test values, hardness (TPA), and rheometric assays. These results indicate that the performance of a cultivar like BP, rendering strong flours, would not be affected when a less strong flour is incorporated up to a certain proportion. However, bread quality of BP was superior to that of KE and BP‐KE blends. The decrease in bread quality was particularly evident in the increase in the shape ratio (W/H). Correlations could be established among some textural parameters of dough (hardness and elasticity) and certain quality attributes of bread (crumb and crust hardness).     

Effect of Moisture Content on the Viscoelastic Properties of Individual Wheat Kernels Evaluated by the Uniaxial Compression Test Under Small Strain

Wheat product quality is related to its physicochemical properties and to the viscoelastic properties of the kernel. The aim of this work was to evaluate the viscoelastic properties of individual wheat kernels using the uniaxial compression test under small strain (3%) to create experimental conditions that allow the use of the elasticity theory to explain the wheat kernel viscoelasticity and its relationships to physicochemical characteristics, such as weight tests, size, and ash and protein contents. The following viscoelastic properties of the kernels of hard and soft wheat cultivars at two different moisture contents (original and tempered at 15%) were evaluated: total work (W_t), elastic work (W_e), plastic work (W_p), and modulus of elasticity (E). There was a significant decrease in W_t as the moisture content increased. In the soft wheat Saturno, W_t decreased 80% (from 0.217 to 0.044 N·mm) as the moisture content increased. Individual wheat kernels at their original moisture content showed higher W_e than under the tempered condition. W_p increased as the moisture content increased. E decreased as the moisture content increased. The soft wheat Saturno showed the highest decline (54.9%) in E (from 14.18 to 6.39 MPa) as the moisture content increased. There were significant negative relationships between the viscoelastic properties and the 1,000‐kernel weight and kernel thickness. The uniaxial compression test under small strain can be applied to evaluate the viscoelastic properties of individual wheat kernels from different classes and cultivars.     

Influence of High Molecular Weight (HMW) and Low Molecular Weight (LMW) Glutenin Subunits Controlled by Glu‐1 and Glu‐3 Loci on Durum Wheat Quality

The progenies of four intervarietal durum wheat crosses were used to determine the effects of glutenin variants coded at Glu‐1 and Glu‐3 loci on durum wheat quality properties. The F₂ lines were analyzed for high molecular weight (HMW) and low molecular weight (LMW) glutenin composition by electrophoresis. Whole grain derived F₃ and F₄ samples were analyzed for vitreousness, protein, and dry gluten contents, gluten index, SDS sedimentation volume, mixograph, and alveograph properties. Allelic variation at the Glu‐B1 and Glu‐B3 loci affected gluten quality significantly. Comparisons among the Glu‐B3 and Glu‐B1 loci indicated that the LMW glutenin subunits controlled by Glu‐B3 c and j made the largest positive contribution, followed by the alleles a, k, and b. HMW glutenin subunits 14+15 gave larger SDS values and higher mixing development times than subunits 7+8 and 20. The positive effects of the glutenin subunits LMW c and HMW 14+15 were additive. Flour protein content, vitreousness, and mixograph peak height values were positively correlated with each other as well as with Dglut values, whereas the SDS sedimentation highly correlated with mixing development time, alveograph strength, and extensibility but was not correlated with the other parameters. The results of quality analysis, together with the results of the genetic analysis, led to the conclusion that SDS sedimentation, mixograph mixing development time, and peak breakdown are the tests more influenced by allelic variation of prolamin. The uses of the results in durum wheat quality breeding programs are discussed.     

Specific Glu‐D1ƒ Allele Frequency of Japanese Common Wheat Compared with Distribution of Glu‐1 Alleles in Chinese Wheat

The quality of wheat (Triticum aestivum L.) grain favored in breadmaking is strongly affected by components of seed storage protein, particularly high molecular weight glutenin subunits (HMW‐GS). The HMW‐GS 2.2 controlled by the Glu‐D1ƒ allele is frequently found in Japanese cultivars and landraces. In the investigation into the factors affecting the distribution of the allele, the available data on HMW‐GS of common wheats from Japan were analyzed and compared with the data for intensity of winter habit and wheat flour hardness. We show that the main factors affecting the Glu‐D1ƒ allele frequency in Japanese wheat were the intensity of natural selection for winter habit and artificial selection for flour hardness. According to a study of the worldwide distribution of Glu‐1 alleles, the Glu‐D1ƒ allele is rare. However, Glu‐D1ƒ allele was the most common Japanese wheat seed storage protein allele. It is well known that Chinese wheat contributed to Japanese landraces, and Japanese landraces contributed to modern cultivars from Japan. However, common Japanese and Chinese wheats differ in the frequencies of Glu‐D1ƒ allele. These results may be explained either by the founder effect or by a selective bottleneck in Japanese common wheat genetic resources.     

Effect of Climate Change on Wheat Quality and HMW Glutenin Subunit Composition in the Pannonian Plain

The primary goal of this study is to improve our understanding of the extent of influence of climatic factors in Serbia and high‐molecular‐weight glutenin subunit (HMW‐GS) composition upon wheat end‐use quality. In‐depth analyses were performed on four bread wheat cultivars that are the most common in agricultural practice in Serbia. Total glutenin content showed significant difference between the production years, in opposition to gliadins. Cluster analysis of different percentages of glutenin and gliadin subunit molecular weight ranges (<40,000, 40,000–80,000, 81,000–120,000, and >120,000) indicated that the year of production and the cultivar did not have a significant effect on the percentage ranges for glutenins. However, they had a considerable impact on the percentage ranges for gliadins. Production year and the interaction of year and cultivar had the strongest influences on the percentage of SDS‐unextractable polymeric proteins. A synergistic effect of the HMW‐GS composition and climatic conditions revealed that all eight samples with HMW‐GS composition 2*, 5 + 10, 7 + 9 along with the highest Glu 1 score of 9 (out of a maximum of 10) produced in the year 2011 belonged to two clusters with the best wheat end‐use quality. Furthermore, the climate conditions in 2011 made it possible for the wheat cultivars with HMW‐GS composition –, 2 + 12, 7 + 9 to possess similar qualities as cultivars with HMW‐GS composition 2*, 5 + 10, 7 + 9 produced in 2012.     

Influence of Low‐Molecular‐Weight Glutenin Subunit Haplotypes on Dough Rheology in Elite Common Wheat Varieties

The low‐molecular‐weight glutenin subunits (LMW‐GSs) are a class of wheat seed storage proteins encoded by a multigene family located at the Glu‐3 loci that influences wheat end‐use quality. Owing to ambiguities in the LMW‐GS allele nomenclature and to the complexity of the Glu‐3 loci organization, a clear relationship between LMW‐GS alleles and wheat end‐use quality has not been adequately determined. In the present study, four sets of elite common wheat varieties were analyzed for their LMW‐GS genic profile, along with their dough rheology and end‐product baking properties. Among these varieties, variation at the Glu‐A3 locus had a major impact on the analyzed dough rheology parameters, followed by the Glu‐B3 and Glu‐D3 loci. Also, the genes located at the linkage groups Glu‐A3‐3, Glu‐B3‐3, and Glu‐D3‐5 were more highly associated with dough strength, mixing, and extensibility properties. Results obtained in this study clearly indicate that there are specific LMW‐GS haplotypes that are more highly associated than others to variation in dough rheology.     

Protein and Quality Characterization of Complete and Partial Near‐Isogenic Lines of Waxy Wheat

The objective of this study was to evaluate protein composition and its effects on flour quality and physical dough test parameters using waxy wheat near‐isogenic lines. Partial waxy (single and double nulls) and waxy (null at all three waxy loci, Wx‐A1, Wx‐B1, and Wx‐D1) lines of N11 set (bread wheat) and Svevo (durum) were investigated. For protein composition, waxy wheats in this study had relatively lower albumins‐globulins than the hard winter wheat control. In the bread wheats (N11), dough strength as measured by mixograph peak dough development time (MDDT) (r = 0.75) and maximum resistance (R_max) (r = 0.70) was significantly correlated with unextractable polymeric protein (UPP), whereas in durum wheats, moderate correlation was observed (r = 0.73 and 0.59, respectively). This may be due to the presence of high molecular weight glutenin subunits (HMW‐GS) Dx2+Dy12 at the Glu‐D1 locus instead of Dx5+Dy10, which are associated with dough strength. Significant correlation of initial loaf volume (ILV) to flour polymeric protein (FPP) (r = 0.75) and flour protein (FP) (r = 0.63) was found in bread wheats, whereas in durum wheats, a weak correlation of ILV was observed with FP (r = 0.09) and FPP (r =0.51). Significant correlation of ILV with FPP in bread wheats and with % polymeric protein (PPP) (r = 0.75) in durum lines indicates that this aspect of end‐use functionality is influenced by FPP and PPP, respectively, in these waxy wheat lines. High ILV was observed with 100% waxy wheat flour alone and was not affected by 50% blending with bread wheat flour. However, dark color and poor crumb structure was observed with 100% waxy flour, which was unacceptable to consumers. As the amylopectin content of the starch increases, loaf expansion increases but the crumb structure becomes increasingly unstable and collapses.     

Rapid Identification of HMW Glutenin Subunits from Different Hexaploid Wheat Species by Acidic Capillary Electrophoresis

High molecular weight glutenin subunits (HMW‐GS) from three hexaploid wheat species (AABBDD, 2n=6x=42, Triticum aestivum L., T. spelta L., and T. compactum L.) were separated and identified by acidic capillary electrophoresis (A‐CE) with phosphate‐glycine buffer (pH 2.5) in uncoated fused‐silica capillaries (50 μm, i.d. × 25.5 cm) at 12.5 kV and 40°C. The rapid separations (<15 min) of HMW‐GS with good repeatability (RSD < 2%) were obtained using a fast capillary rising protocol. All 17 HMW‐GS analyzed could be well separated and their relative migration orders were ranked. In particular, the good quality subunit pair 5+10 could be differentiated from poor quality subunit pair 2+12. In addition, the other three allelic pairs of 13+16, 17+18, and 7+8 subunits that were considered to have positive effects on dough properties, as well as three pairs of novel subunits 13+22*, 13*+19*, and 6.1+22.1 detected from spelt and club wheat, can also be readily separated and identified. An additional protein subunit presented in Chinese bread wheat cultivar Jing 411 and club wheat TRI 4445/75, respectively, was detected by both A‐CE and 2‐D gel electrophoresis (A‐PAGE × SDS‐PAGE), for which further identification is needed.     

Relationships of High Molecular Weight Glutenin Subunit Composition and Molecular Weight Distribution of Wheat Flour Protein with Water Absorption and Color Characteristics of Noodle Dough

Colors of noodle doughs made from hard white winter wheat flours from Oregon were measured at optimum noodle water absorptions (NWA). Partial correlations, removing effect of protein concentration, indicated that NWA had negative relationships with 0 hr L* and 24 hr b*, and positive relationships with 0 and 24 hr a*. Kernel hardness index had positive simple and partial correlations with NWA without any significant (P < 0.05) correlation with color parameters. High molecular weight glutentin subunits (HMW‐GS) significantly (P < 0.05) affected all measured noodle parameters except for 0 hr L*. Covariance analysis, using protein concentration as a covariate, indicated that HMW‐GS significantly affected NWA and a* (P < 0.01). Wheat cultivars with HMW‐GS 17+18 showed significantly higher mean NWA and a* values than those with alternative Glu‐B1 subunits. Protein molecular weight distributions affected noodles, as shown by significant correlations with absorbance areas and % areas of protein size exclusion (SE) HPLC chromatograms. Protein fractions that had positive correlations with redness had negative correlations with yellowness. Applying multivariate analyses to SE‐HPLC data to derive calibration models to predict fresh noodle dough a* and b* values had R² > 0.91 and cross validations values of R² > 0.75.     

Effect of High‐Molecular‐Weight Glutenin Subunit Allelic Composition on Wheat Flour Tortilla Quality

Wheat cultivars possessing quality attributes needed to produce optimum quality tortillas have not been identified. This study investigated the effect of variations in high‐molecular‐weight glutenin subunits encoded at the Glu‐1 loci (Glu‐A1, Glu‐B1, and Glu‐D1) on dough properties and tortilla quality. Flour protein profiles, dough texture, and tortilla physical quality attributes were evaluated. Deletion at Glu‐D1 resulted in reduced insoluble polymeric protein content of flour, reduced dough compression force, and large dough extensibility. These properties produced very large tortillas (181 mm diameter) compared with a control made with commercial tortilla wheat flour (161 mm). Presence of a 7 + 9 allelic pair at Glu‐B1 increased dough strength (largest compression force, reduced extensibility, and small‐diameter tortillas). Deletion at Glu‐A1 produced large tortillas (173 mm) but with unacceptable flexibility during storage (score <3.0 at day 16). In general, presence of 2* at Glu‐A1, in combination with 5 + 10 at Glu‐D1, produced small‐diameter tortillas that required large force to rupture (tough texture). Presence of 2 + 12 alleles instead of 5 + 10 at Glu‐D1 produced tortillas with a good compromise between diameter (>165 mm) and flexibility during storage (>3.0 at day 16). These allele combinations, along with deletion at Glu‐D1, show promise for tortilla wheat development.     

Quality and Agronomic Effects of Three High‐Molecular‐Weight Glutenin Subunit Transgenic Events in Winter Wheat

Quality and agronomic effects of three transgenic high molecular weight glutenin subunit (HMW‐GS) events were characterized in advanced‐generation breeding lines of hard winter wheat (Triticum aestivum L.) in three Nebraska crop years. Two of the transgenic events studied, Dy10‐E and B52a‐6, overexpress HMW‐GS 1Dy10, while the third event, Dx5 +Dy10‐H, overexpresses HMW‐GS 1Dx5 and, to a much lesser extent, 1Dy10. In addition, novel proteins possessing solubility characteristics defined as HMW‐GS were present in Dx5+Dy10‐H and B52a‐6. Average grain yield of lines derived from the three transgenic events was statistically lower than that of a group of control cultivars and advanced breeding lines, but not lower than the mean values of respective nontransgenic siblings. Grain hardness was influenced by one of the events. Dx5+Dy10‐H produced harder kernels than controls, its nontransgenic siblings, and the two additional transgenic events. All three events produced doughs with unusual mixing properties, although not likely to be directly useful in commercial applications. As a consequence, loaf volumes were depressed to variable degrees by the three events. The results indicated that over‐expression of HMW‐GS could eventually lead to improved breadmaking quality by optimizing the level of overexpression or by development and characterization of additional events.     

Genetic Variance for Gluten Strength Contributed by High Molecular Weight Glutenin Proteins

A total of 162 doubled haploid (DH) lines were produced from a cross between Triticum aestivum L. ‘AC Karma’ and line 87E03‐S2B1 to study the genetic contribution of high molecular weight (HMW) glutenin subunits to gluten strength. HMW glutenin subunit composition of each DH line was determined by SDS‐PAGE. The population was grown in the field at one location in 1999 and at three locations in 2000. Gluten strength and dough mixing properties were measured by mixograph test and SDS‐sedimentation test. Variance components were estimated for each measurement to determine the variability contributed by HMW glutenin subunits. Results indicated significant environmental impact on tested mixograph parameters, SDS‐sedimentation volumes and grain and flour protein concentration. Significant main effects of Glu‐1D loci encoded subunits were obtained for mixograph development time, energy to peak, slope after peak, and first minute slope. Lines containing 5+10 combination of subunits had higher values for mixograph development time and energy to peak, while slope after peak and first minute slope were lower as compared with 2+12 containing lines. Low intergenomic interactions were observed for bandwidth energy (BWE), total energy (TEG), and SDS‐sedimentation test, involving B and D genomes only. A portion of the genetic variability for gluten strength was accounted for overexpression of Bx7 subunit originating from the cultivar Glenlea derived line 87E03‐S2B1. There was no significant effect of Glu‐A1 encoded subunits on any of the tested parameters. Estimated genetic variability for gluten strength contributed by Glu‐B1 and Glu‐D1 encoded HMW glutenins was 55% for mixing development time and 51% for energy to peak.     

Expression,Purification, and Functional Analysis of Three Low‐Molecular‐Weight Glutenin Subunits from Wheat Cultivar Cheyenne

Glutenins, which form the network of gluten protein, are of great importance for the quality of flour products. Glutenins can be divided into HMW and LMW subunits according to molecular weight. Three genes for LMW glutenin subunits (LMW‐GS), named lmw‐cnd1, lmw‐cnd2, and lmw‐cnd3 with open reading frames of 1,053, 903, and 969 bp, respectively, were cloned from wheat cultivar Cheyenne. Heterologous expression vectors of the three LMW‐GS were constructed, and the recombinant proteins LMW‐CND1, LMW‐CND2, and LMW‐CND3 were overexpressed in Escherichia coli. After cell disruption with ultrasound, target proteins of high purity were obtained by using Ni²⁺ affinity chromatography. Farinograph and TAPlus measurements were used to investigate the effects of the three LMW‐GS on the characteristics of flour and dough. The results showed that the addition of each LMW‐GS can lead to an increase in the elasticity of the dough. Moreover, LMW‐CND2 and LMW‐CND3 promoted the strength of the dough. All three LMW‐GS caused a decrease of hardness and increase of springiness and cohesiveness of dough according to texture profiling results. Consequently, all three LMW‐GS have positive effects on the processing characteristics of dough and can improve bread quality to different extents.