Bread making quality of durum wheat genotypes with some novel glutenin subunit compositions

Durum wheat genotypes with some novel high M_r (high molecular weight, HMW) and low M_r (low molecular weight, LMW) glutenin subunits were grown in Sicily for two years of testing in order to compare their rheological and baking properties with respect to commercial durum wheat cultivars. Good bread making quality, as measured by Alveograph W and P/L, Farinograph and Mixograph parameters, and loaf volume was observed in genotypes combining high M_r subunits 2⁺, 1 or 11 encoded at the Glu-A1 locus with the so-called LMW-2 subunit group encoded at the Glu-B3 locus. The cultivar Avanzi, which carries high M_r subunit 2⁺ and LMW-2-like subunits, and the cultivars Dritto and Keops, which contain novel high and low M_r subunits, gave higher loaf volumes than control cultivars. The LMW-2 group subunits were found to be the main factor in determining dough strength (Alveograph W). The increase in the amount of high M_r subunits in genotypes with one expressed Glu-A1 gene may account for their improved rheological and baking properties.     

Glutenin subunit compositions and breadmaking quality characteristics of synthetic hexaploid wheats derived from Triticum turgidum × Triticum tauschii (coss.) Schmal Crosses

The Glu-B1, Glu-D1 and Glu-B3 encoded glutenin subunit compositions of a population of synthetic hexaploid wheats (AABBDD, 2n=6x=42), which was random for flour protein (FP), SDS-sedimentation (SDSS), Alveograph strength (W), the tenacity/extensibility (P/G) ratio and bread loaf volume (LV) were examined in this study. The synthetics were produced from various crosses involving several Triticum lurgidum cultivars and Triticum lauschii (coss.) Schmal accessions. The Glu-A1 null allele as well as three Glu-B1 (subunits 7 + 8, 6 + 8 and 20), 13 Glu-D1 and two Glu-B3 (LMW-1 and LMW-2) allelic variants were present in the synthetic population. Thirty-six different glutenin subunit combinations, including the Glu-B1, Glu-D1 and Glu-B3 encoded alleles, were observed. The synthetic hexaploids showed large variations for all quality parameters evaluated. All quality characteristics except one (P/G ratio, which showed no association with allelic variations at Glu-B3) were influenced by allelic variations at the Glu-B1 and Glu-B3 loci; subunits 6 + 8 and 7 + 8 showed significantly better quality effects than subunit 20. Low M_r glutenin subunits LMW-1 and LMW-2 showed both negative and positive quality effects. The Glu-D1 locus of T. tauschii contributed various alleles not found in bread wheat. The influence of new Glu-D1 alleles on the bread-making quality characteristics of the synthetic wheats could not be established, partly because there was a limited frequency of some of the alleles in the population, and partly because some synthetics, having a common Glu-D1 allele, showed quality differences associated with allelic variation at Glu-B1 and/or Glu-B3. Differential quality effects could be observed, however, among some Glu-D1 alleles. Synthetics derived from a common durum wheat source showed better overall quality characteristics and bread loaf volume when they possessed subunits 5 + 12 or 1·5 + 10 than when they had any other Glu-D1 encoded glutenin subunit.     

Composition of polymeric proteins and bread-making quality of wheat lines with allelic HMW-GS differing in number of cysteines

Three lines of Australian wheat variety Avocet, two biotypes of Australian variety Halberd, and the Italian bread wheat cultivar Fiorello and its derived line were used to study the possible role of the Glu-B1 HMW-GS in polymeric protein composition and flour functionality. These sets of lines contain HMW-GS 7+8, 7+9, 20x+20y or 26+27. Subunit Bx7 has four cysteine residues, while subunit Bx20 has only two. Compared to Avocet A (7+8), line Avocet C (20x+20y) exhibited an increase in polymeric protein, a decrease in the gliadin-to-glutenin ratio, and a marked decrease in unextractable polymeric protein (UPP). Avocet C doughs exhibited greater extensibility and shorter Mixograph dough development times, and baked into smaller loaves compared to those from Avocet A. Similar differences were observed in comparisons between the two Fiorello lines and between the two Halberd biotypes that had differing Glu-B1 alleles. These results show that in closely related genotypes, the presence of the Bx7+By8 or Bx7+By9 HMW-GS instead of Bx20+By20 or Bx26+By27 is associated with higher UPP, higher dough strength and better bread-making performance. It is suggested that this could be due to the greater number of cysteines in the Bx7 subunit that are available for forming higher-molecular-weight glutenin polymer. This could give the possibility to manipulate dough properties and bread-making quality by utilizing HMW-GS alleles with varying numbers of cysteine residues.     

Functional Properties of Wheat Glutenin

The importance of glutenin in bread-making quality has led to a substantial research effort. Studies on glutenin can be grouped into four categories: studies that determine the statistical relationships between the quantity of fractions and quality, studies of reconstitution and fortification, breeding and genetic modification, and those that assess structure–function relationships during processing. Statistical relationships between glutenin, glutenin fractions and glutenin polypeptides and quality have been established. The SDS or acetic acid unextractable glutenin correlated strongly with quality parameters. For highM_rglutenin subunits the relationships with quality are less strong. In some studies it was demonstrated that the presence of some highM_rglutenin subunits is correlated with the quantity of unextractable glutenin. Therefore, subunits are probably indirectly linked with bread-making qualityviathe quantity of unextractable glutenin. Recombination and fortification studies are hampered by changes in functionality of proteins after their separation. Recently, small scale tests have been developed in which small amounts of glutenin fractions can be studied. Controlled breeding studies have demonstrated the importance of highM_rglutenin subunits 5+10 and, to a lesser extent, 1 or 2* for quality. In most of these studies the quantity of unextractable glutenin is not reported. This hampers adequate conclusions on cause–effect relationships. During dough processing large changes occur in the extractability of glutenin. The significance of these changes for dough properties and bread quality still requires investigation.     

High Mr Glutenin Subunits of Indian Wheat Cultivars: Association of Subunits 5 + 10 with the 1BL/1RS Wheat-Rye Translocation

The seed proteins of 110 commercially-released Indian wheat cultivars were fractionated using sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) to determine their high M_r glutenin subunit compositions. Amongst the cultivars, three alleles were indentified for the Glu-A1 locus (subunits 1, 2^* and the null phenotype), eight alleles for the Glu-B1 locus (7, 7 + 8, 7 + 9, 6 + 8, 20, 13 + 16, 17 + 18 and a new allele) and two for the Glu-D1 locus (2 + 12 and 5 + 10). Nine of the cultivars were heterogeneous and possessed two or more 'biotypes' with respect to high M_r subunits. The cultivars were also analysed for the presence of the 1BL/1RS wheat-rye translocation by SDS-PAGE of unreduced prolamins and hybridisation of DNA dot blots with a rye-telomere-specific repetitive DNA probe, pAW-161. Both methods revealed that the majority of newly-released Indian wheat cultivars carry this translocation, thus confirming the agronomic superiority of these lines. While most of the normal wheat cultivars possessed high M_r subunits 2 + 12, 14 of the 18 translocation cultivars had the allelic subunits 5 + 10, even though no selection was made for these subunits during the breeding process. This suggests that the subunits 5 + 10 may play a compensating role for the loss of dough strength associated with the 1BL/1RS translocation.     

Functional Properties of LowMrWheat Proteins.III. Effects on Composition of the Glutenin Macropolymer During Dough Mixing and Resting

The effect of lowM_rwheat protein addition on the amount and composition of the glutenin macropolymer (GMP) of dough was investigated for the three wheat cultivars Obelisk (weak), Camp Remy (medium strong) and Rektor (strong). During mixing, the amounts of high and lowM_rglutenin subunit classes, and of the individual subunits decreased. The proportion of highM_rglutenin subunits decreased and that of lowM_rglutenin subunits increased, indicating an inhomogeneous distribution of the two subunit classes within the polymers present in GMP. During resting, the amounts of the glutenin subunit classes and of individual subunits increased. Meanwhile, the proportion of highM_rglutenin subunits in GMP increased. LowM_rwheat protein addition retarded re-polymerisation in that the amounts of glutenin subunit classes and of individual highM_rglutenin subunits in GMP increased less than without addition. The proportion of highM_rglutenin subunits in GMP directly after mixing was also decreased by lowM_rwheat protein addition, and the proportion increased faster during dough resting, compared with the GMP in dough without lowM_rwheat protein addition. Eventually, after 90 or 135 min resting, no differences existed in the proportions in GMP from doughs with and without lowM_rwheat protein addition. LowM_rwheat protein addition had no specific effect on individual highM_rglutenin subunits, nor on the x-type/y-type subunit ratio in the GMP. In contrast, with increasing lowM_rwheat protein addition, a highly significant reduction in the subunit 10 or 12/subunit 9 ratio in GMP was observed. This finding is in line with the decrease in this ratio directly after mixing in GMP of the dough without lowM_rwheat protein addition. Since no specific effects were observed, it can be concluded that the lowM_rwheat protein acts rather unspecifically on the GMP of dough.     

Quality-related Epitopes of High Mr Subunits of Wheat Glutenin

Three hundred and eighty four immobilised overlapping nonapeptides, corresponding to the full amino acid sequences of three high M_r subunits of glutenin from bread wheat (Triticum aestivum) grain, were used to determine the linear epitopes recognised by four monoclonal antibodies. These antibodies were selected on the basis of significant and positive correlations between their binding to wheat flour extracts in a two-site ('sandwich') enzyme immunoassay and rheological measures of dough strength, an important aspect of bread wheat quality. The antibodies did not bind to a single, specific sequence but bound a series of related peptides in each high M_r glutenin subunit examined. The sequences recognised were not identical for the four antibodies, but in each case were in the central repeating domain of the high M_r glutenin subunits, and usually comprised regions that overlapped the degenerate repeat nonamer and hexamer sequences. High M_r glutenin subunits that have been associated with greater dough strength, such as the D-genome allelic products 1Dx5 and 1Dy10, displayed an increased number of the epitope sequences. The location of the epitopes in sequences of overlapping β-turns in the repetitive region supports the hypothesis that dough elasticity arises partly from β-turn-forming secondary structure in the repeat regions of the M_r glutenin subunits. Additional β-turn within high M_r subunits may extend their structure to allow increased interaction between the glutenin subunits and with the other proteins of the gluten complex, thus improving dough strength.     

Effect of Allelic Variation of Glutenin Subunits and Gliadins on Baking Quality in the Progeny of Two Biotypes of Bread Wheat cv. Ulla

During the determination of the HMW glutenin subunit composition of Finnish varieties, the variety Ulla was observed to contain two biotypes which differed from each other at two loci:Glu-A1andGlu-A3/Gli-A1. One of them, called Ulla 1, contained subunit 2* (Glu-A1b) andGlu-A3o/Gli-A1o, and Ulla 2 contained the null allele (Glu-A1c) andGlu-A3a/Gli-A1c. In order to determine the effect of this allelic variation on quality, the two biotypes were crossed and random lines were produced from the progeny by single seed descent. In total, 95 F6 lines were analysed from four bulked Ulla progeny lines. Significant interaction between the allelic variants of HMW glutenins and LMW gluten proteins affected the SDS-sedimentation volume at the mean flour protein level of 13·1% (dmb); the effect of LMW gluten variants was larger in the lines deficient of a HMW glutenin subunit than in lines having a HMW glutenin subunit (2*). At the higher flour protein levels (mean=15·1%, dmb) the effect on SDS-sedimentation volume was additive; progeny carrying alleles b (subunit 2*) and o/o atGlu-A1andGlu-A3/Gli-A1had significantly greater sedimentation volumes than the progeny carrying alleles c (no subunit) and a/c, respectively. The SDS-sedimentation volumes indicated differences in the quantities of the polymeric glutenins, gel proteins which have been shown to reflect dough strength. In the four bulked Ulla progeny lines, the variation in HMW glutenin subunits affected the dough strength values of the Extensigraph. However, the variation in LMW glutenin subunits did not affect Extensigraph dough strength values, as was predicted by SDS-sedimentation volumes. In the Ulla progeny, adding a HMW glutenin subunit affected Extensigraph dough strength more than adding a LMW glutenin subunit, although both increased the SDS-sedimentation volumes. Moreover, the variation in LMW gluten proteins affected the dough mixing stability in the Farinograph and test baking results of the Ulla progeny.     

Characterisation of polyclonal and monoclonal anti-peptide antibodies specific for some lowMrsubunits of wheat glutenin and their use in the detection of allelic variants atGlu-3loci

Polyclonal and monoclonal antibodies (Mabs) were produced against the major type ofN-terminal amino acid sequence of lowM_rglutenin subunits. The reactivities of these antibodies were determined using glutenin extracts of several bread wheat cultivars of known allelic composition. Analyses were performed by immunoblotting after one or two-dimensional electrophoresis. One Mab (Mab 6x1) was found to react with lowM_rglutenin subunits encoded by chromosomes 1B and 1D but not with subunits controlled by chromosome 1A. Only some of the subunits encoded at theGlu-D3locus were recognised. In contrast, this Mab reacted with all the subunits controlled by theGlu-B3locus. After single dimension SDS–PAGE, we observed significant differences between immunoblot patterns of cultivars expressing different lowM_rglutenin subunits from chromosome 1B. Mab6 x1 is a useful reagent for analysing the allelic composition at theGlu-B3locus.     

Effect of the 1BL.1RS translocation and of the Glu-B3 variation on fifteen quality tests in a doubled haploid population of wheat (Triticum aestivum L.)

To investigate the impact of 1BL.1RS translocation on protein content, starch quality, dough rheology, RMT volumes and other quality traits, a doubled haploid population was created and sown in a two-year field experiment. Translocated genotypes accumulated more proteins in the endosperm than non-translocated genotypes. Decrease in the gelatinization of starch was associated with the 1BL.1RS translocation. As for rheological parameters, adapted to bread types not requiring high mixing energy, the 1BL.1RS translocation significantly reduced the elasticity, tenacity and strength of the dough compared to allele c of Glu-B3. Tolerance to over-mixing was also significantly lower in translocated DH lines. In contrast to previously published work, the presence of allele Glu-D3 c resulted in significantly higher tenacity, and thus strength, compared with the allele Glu-D3 b in the present DH population. The final baking test performed on the DH lines of the population, combining favourable alleles for dough rheology and high protein content, demonstrated that in some cases lower tenacity induced by the 1BL.1RS translocation or by Glu-B3 b increases the volume of the loaves.     

A Null Gli-D1 Allele with a Positive Effect on Bread Wheat Quality

The French wheat cultivar Darius (Da) has very good bread-making quality, even though it possesses the high M_r glutenin subunit combination 2, 7 and 12, which is associated with poor quality, and a null allele at the Gli-D1 locus. Darius was crossed with three cultivars, Corin (Cor), Capitole (Cap) and Courtot (Cou), of poor, medium, and good quality, respectively. The three progenies (Cor × Da, Cap × Da and Da × Cou) were used to investigate the genetic basis of the good quality of Darius. Gliadin and glutenin compositions were analysed by acid polyacrylamide gel electrophoresis (A-PAGE) and SDS-PAGE, respectively, from half F2 grains, and the quality was evaluated using six technological criteria for the corresponding plants. The high M_r glutenin subunit alleles of Darius produced a negative effect on quality. The null allele of Darius, characterised by the absence of the Gli-D1 encoded ω-gliadins, was associated significantly with higher dough tenacity P , and strength W (up to 40% in the Cor × Da progeny). Darius had a higher amount of B zone low M_r glutenin subunits than the three other cultivars. The null allele of Darius reduced the dough extensibility in the two first progenies, and probably increased the ratio of aggregated glutenin to unaggregated gliadins. These results demonstrated that using only one locus breeders can improve particular quality traits.     

青海高原春小麦HMW—GS等位基因变异及其对面团流变学特性的作用

为了给青海高原春小麦改良提供资料。分析了青海育成和国内外引进的125个春小麦品种(系)的HMW—GS等位基因变异。并测定了其中58个品种(系)在青海高原环境下的面团流变学特性。结果表明：(1)参试春小麦品种(系)的HMW—GS存在广泛的变异。Glu—A1位点出现3个等住基因，Glu—B1住点出现5个等住基因，Glu—D1位点出现4个等位基因；共出现了22种HMW—GS组合形式。其中1.7 8.2 12和N，7 8，2 12组合类型出现频率最高。并发现了个别罕见的变异类型，如2 10，10。(2)亚基组合类型对沉淀值、形成时间、稳定时间、评价值等品质性状影响较大，对籽粒蛋白质含量、出粉率和面粉吸水率的影响不显著。试验还表明，HMW—GS组成与面粉的筋力有密切关系。     

Separate effects on gluten strength of Gli-1 and Glu-3 prolamin genes on chromosomes 1A and 1B in durum wheat

Two recombinants between Gli-A1 and Glu-A3 prolamin genes and seven between Gli-B1 and Glu-B3 obtained from two crosses of durum wheat were classified on the basis of the prolamin alleles at the Glu-A1, Gli-A1, Glu-A3, Gli-A2, Glu-B1, Gli-B1 and Glu-B3 loci. The separate effects on gluten strength of gliadin genes at Gli-1 and low M_r glutenin subunit genes at Glu-3 were estimated by comparing the SDS-sedimentation test values of the recombinants with those of the same progeny having the same prolamin composition, except for the recombined alleles. The results showed clearly that low M_r glutenin subunit genes at Glu-A3 and Glu-B3, rather than gliadin genes at Gli-A1 and Gli-B1, were responsible for the differences in gluten strength.     

Depolymerisation and Re-polymerisation of Wheat Glutenin During Dough Processing. I. Relationships between Glutenin Macropolymer Content and Quality Parameters

The protein content and the content of protein-related parameters of both flour and dough were related to the maximum resistance (R_max) and extensibility (E) of dough, as determined in a Brabender Extensograph, and to loaf volume. The glutenin macropolymer (GMP) content of flour and dough was more strongly related toR_maxthan protein content or the content of the group of Osborne fractions (glutenin, gliadin, albumin/globulin). Within each group of protein-related parameters, the contents of the Osborne glutenin fractions explained the variation in all quality parameters better than the contents of the gliadin or albumin/globulin fraction. The GMP content of dough after 45 min rest was more strongly related toR_max, whereas the GMP content of flour was more strongly related toEand loaf volume. This demonstrates that, during mixing and resting of dough, changes occur in the GMP that are important forR_maxbut not forEor loaf volume. Although limited numbers of wheat cultivars (15), harvest years (2), flour blends (8) and resting times (3) were investigated, the relationship between the GMP content of dough andR_maxwas independent of these variables.     

Factors Governing Levels and Composition of the Sodium Dodecyl Sulphate-Unextractable Glutenin Polymers During Straight Dough Breadmaking

The effect of several additives (1·215 μmol KIO₃, 0·892 μmol cysteine, endo-xylanase and 0·5% (w/w) rye-water-extractable arabinoxylans) on changes in the level and glutenin subunit composition of the sodium dodecyl sulphate (SDS)-unextractable protein during breadmaking was investigated. Protein extractability drastically increased during dough mixing and was enhanced both by cysteine and KIO₃. The mixing-induced increase in protein extractability was partly reversed during fermentation. Fermenting doughs containing endo-xylanase had a higher level of SDS-unextractable protein than control doughs, while with KIO₃the amount of SDS-unextractable protein remained very low. During baking most protein became SDS-unextractable. Bread baked from doughs with added KIO₃contained a significantly higher level of SDS-extractable protein. Changes in subunit composition of the SDS-unextractable glutenin polymers, determined with RP-HPLC, coincided with changes in protein extractability during dough processing. Mixing decreased the ratio of high to lowM_rglutenin subunits. Simultaneously, the relative proportions of the different highM_rglutenin subunits in the unextractable glutenin polymers changed. During fermentation changes in subunit composition of the SDS-unextractable glutenin were opposite to those during mixing.     

New B low Mr glutenin subunit alleles at the Glu-A3, Glu-B2 and Glu-B3 loci and their relationship with gluten strength in durum wheat

The B low M_r subunits of glutenin of the F₂ generation from three durum wheat crosses were analysed. Three new alleles were found at three different loci: Glu-A3i coding for 5+20 subunits, Glu-B2c coding for subunit 12* and Glu-B3l coding for 1+3+13*+16 subunits. The genetic distances between Glu-A3-Gli-A1, Glu-B2-Gli-B1, Glu-B3-Glu-B2 and Glu-B3-Gli-B1 were calculated. The effects of the allelic variation at the Glu-A3, Glu-B2 and Glu-B3 on protein content and gluten strength, as measured by the SDS-sedimentation test, were determined using F₄ lines from the three crosses. All the new alleles affected significantly gluten strength. The presence of Glu-A3i had a negative influence on SDSS values compared with the allele a. For Glu-B2 and Glu-B3 the data obtained enable the effects of the alleles on SDSS volume to be ranked: a=b>c for Glu-B2 and a>b>l for Glu-B3. The results also shown that the allelic variants at Glu-B3 had a much greater effect on gluten strength than the variants at Glu-A3 or Glu-B2 loci. A high percentage of variation in sedimentation volume was explained by the prolamins (52 and 70%).     

Development of introgression lines with 18 alleles of glutenin subunits and evaluation of the effects of various alleles on quality related traits in wheat (Triticum aestivum L.)

In this report, we present a set of 104 ILs with 18 alleles for five glutenin loci. They were developed from crossing and backcrossing 64 varieties as donor parents to Yanzhan 1 as recurrent parent. The effects of the 18 alleles on nine dough quality parameters were evaluated in a similar background using these lines. The results showed that Glu-A1a produced the highest SDS-sedimentation volume (Ssd), midline time x=8 width (MTxW), mixing tolerance (MT) and the lowest weakening slope (WS). At the Glu-B1 locus, Glu-B1f produced the highest values for all quality parameters but WS. At the Glu-D1 locus, Glu-D1d was the best for Ssd, grain hardness (GH), midline peak width (MPW), MTxW and MT. The positive effects of Glu-B1f on GH and Glu-B3b on Ssd were mainly from the effect of GPC. Overall, 5 interactive loci and 13 interactive alleles were found to be significant. No negative interaction between high quality glutenin alleles was detected. The preferred allele combinations for breeding were recommended based on the additive and interactive effects. Our results suggest that the ILs with multiple alleles are ideal genomic stocks for evaluating the effects of alleles on some traits and for pyramiding favorable alleles in breeding wheat varieties.     

Effect of the 1BL.1RS translocation and of the Glu-B3 variation on fifteen quality tests in a doubled haploid population of wheat (Triticum aestivum L.)

To investigate the impact of 1BL.1RS translocation on protein content, starch quality, dough rheology, RMT volumes and other quality traits, a doubled haploid population was created and sown in a two-year field experiment. Translocated genotypes accumulated more proteins in the endosperm than non-translocated genotypes. Decrease in the gelatinization of starch was associated with the 1BL.1RS translocation. As for rheological parameters, adapted to bread types not requiring high mixing energy, the 1BL.1RS translocation significantly reduced the elasticity, tenacity and strength of the dough compared to allele c of Glu-B3. Tolerance to over-mixing was also significantly lower in translocated DH lines. In contrast to previously published work, the presence of allele Glu-D3 c resulted in significantly higher tenacity, and thus strength, compared with the allele Glu-D3 b in the present DH population. The final baking test performed on the DH lines of the population, combining favourable alleles for dough rheology and high protein content, demonstrated that in some cases lower tenacity induced by the 1BL.1RS translocation or by Glu-B3 b increases the volume of the loaves.     

Association analysis reveals effects of wheat glutenin alleles and rye translocations on dough-mixing properties

The glutenin loci of wheat (Triticum aestivum L.) are important determinants of bread-making quality, although the effects of alleles at those loci are incompletely understood. We applied an association analysis method to assess the effects of glutenin alleles and 1RS wheat–rye (Secale cereale L.) translocations on dough-mixing properties in 96 wheat cultivars and advanced lines grown at three Colorado locations while accounting for population structure and relatedness of individuals in the population. The results indicated that (1) in the majority of cases, controlling relatedness of individuals reduced the significance of associations between glutenin loci and Mixograph traits; (2) the Glu-D1 and Glu-B3 loci and 1RS translocations had greater impacts on dough-mixing properties compared to other glutenin loci; (3) Glu-B1w, Glu-D1d, and Glu-B3b were consistently associated with greater (more favorable) Mixograph peak time (MPT) than other alleles at the respective loci, whereas Glu-B1e, Glu-D1a, and Glu-B3c were associated with reduced MPT; (4) the 1BL.1RS translocation was associated with a decrease in Mixograph properties. Our results indicate that taking multiple-level relatedness of individuals into account can improve the results of association analysis for wheat-quality traits.