Effect of allelic variation at the Glu-3/Gli-1 loci on breadmaking quality parameters in hexaploid wheat (Triticum aestivum L.)

Low molecular weight glutenin subunits (LMW-GS) encoded by the Glu-3 loci are known to contribute to wheat breadmaking quality. However, the specific effect of individual Glu-3 alleles is not well understood due to their complex protein banding patterns in SDS-PAGE and tight linkage with gliadins at the Gli-1 locus. Using DNA markers and a backcross program, we developed a set of nine near isogenic lines (NILs) including different Glu-A3/Gli-A1 or Glu-B3/Gli-B1 alleles in the genetic background of the Argentine variety ProINTA Imperial. The nine NILs and the control were evaluated in three different field trials in Argentina. Significant genotype-by-environment interactions were detected for most quality parameters indicating that the effects of the Glu-3/Gli-1 alleles are modulated by environmental differences. None of the NILs showed differences in total flour protein content, but relative changes in the abundance of particular classes of proteins cannot be ruled out. On average, the Glu-A3f, Glu-B3b, Glu-B3g and Glu-B3i_Man alleles were associated with the highest values in gluten strength-related parameters, while Glu-A3e, Glu-B3a and Glu-B3i_Chu were consistently associated with weak gluten and low quality values. The value of different Glu-3/Gli-1 allele combinations to improve breadmaking quality is discussed.     

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%).     

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.     

Effects of different prolamin alleles on durum wheat quality properties

The F₄ progenies of four durum wheat crosses were used to determine the effects of different prolamin alleles on quality properties evaluated by the SDS sedimentation, mixograph, micro-alveograph and vitreousness tests and by protein content. Allelic compositions of the gliadins (Gli-B1 and Gli-2 loci) and the glutenins (Glu-1, Glu-3 and Glu-B2 loci) were determined. Alleles at the Glu-B3 locus showed a strong influence on quality measured by SDSS, mixograph and alveograph tests. Significant interactions between Glu-B3 and other glutenin loci were also detected. Prolamin composition explained more than 30% of the variation in SDSS, mixograph MT and alveograph W. The mixograph parameter BDR, and alveograph P and L parameters were the most erratic with between 8 and 76% of variation explained by prolamin composition. In general, no significant associations of prolamins with vitreousness or protein content were found. A significant correlation was detected between SDSS, MT and W. These results together with those from previous studies have important implications for wheat breeders since selection based on good alleles at Glu-B3 (a, c, j) together with favourable alleles at other loci such as Glu-A1 (subunit 1), Glu-A3 (a, c, d, h), Glu-B2 (a,b) and Gli-B1 (ω-35) could improve durum wheat quality.     

Relationships Between Chromosome 1B-encoded Glutenin Subunit Compositions and Bread-making Quality Characteristics of Some Durum Wheat (Triticum turgidum) Cultivars

The high and low M_r glutenin subunit compositions (controlled by the Glu-1 loci and the Glu-B3 locus, respectively) and the bread-making quality characteristics of 26 durum wheat (Triticum turgidum) genotypes were determined. The relationships between quality parameters and Glu-B1 and Glu-B3 controlled glutenin subunit composition were also investigated. The Glu-A1-controlled null allele was present in all the genotypes. High M_r subunits 20, 6 + 8 and 7 + 8 occurred in similar proportions in the cultivars analysed. The Glu-B3 low M_r allelic variants, LMW-1 and LMW-2, were both represented, with LMW-1 being present in lower proportion. Flour protein, SDS-sedimentation volume, dough strength (Alveograph W value), dough mixing time and bread loaf volume varied among the genotypes. Most samples had high Alveograph tenacity/extensibility (P/G) ratios, typical of tenacious gluten character. SDS-sedimentation volume, dough strength, dough mixing time and bread loaf volume were all interrelated. An association with flour protein content was observed only for mixing time, while the Alveograph tenacity/extensibility ratio was not correlated with the other parameters. Comparisons within the Glu-B1 and Glu-B3 loci indicated that the high M_r subunit 7 + 8 and the low M_r subunit LMW-2 had significantly greater beneficial effects on gluten strength and bread-making quality than the high M_r subunits 6 + 8 or 20 and the low M_r subunit LMW-1, respectively. High M_r subunit 6 + 8 had greater beneficial effects on quality than subunit 20.     

Relationship Between Gliadin Alleles and Dough Strength in Italian Bread Wheat Cultivars

Dough strength, as determined by Alveograph W, was studied in Italian bread wheat cultivars grown at several locations over 21 years of testing. Broad sense heritability of Alveograph W was found to range between 0·40 and 0·82, variation in this parameter being affected by genotype×year interactions. Standardised Alveograph W values (Wst) across 40 environments (location–year combinations) were computed for 54 cultivars with reference to the long-term control (cv. Mec), and a quality score based on the Wst value was given to each gliadin allele occurring in at least four of the 54 cultivars analysed. Significant differences in Wst values were observed at theGli-B1,Gli-B2andGli-A2loci. AllelesGli-B1b,Gli-B2candGli-A2bwere significantly related to high gluten strength. An overall quality score based on allelic composition at these loci explained 41% of the observed Wst variation in the 54 cultivars used for the score definition, and 23% to 48% of W value variation in three sets of independent data. The combination of this score with a quality score based onGlu-1alleles coding for highM_rglutenin subunits could explain, on average, about 50% of gluten strength variation.     

Thermal stability of wheat gluten protein: its effect on dough properties and noodle texture

There is a need to develop more sensitive and reliable tests to help breeders select wheat lines of appropriate quality. Gluten thermostability, measured by the viscoelasticity of heated gluten, was assessed for its usefulness in evaluating quality of wheats in breeding programs. Two sets of wheat samples were used: Set I consisting of 20 cultivars and/or breeders' lines (BL), with diverse dough strengths and allelic variations of high M_r glutenin subunits coded at the Glu-A1, Glu-B1 and Glu-D1 loci (N=20) and Set II consisting of 16 near isogenic BL of F7 generation that had been in a quality selection program for three years. Thermostability of the isolated wet gluten was determined by measuring its viscoelastic properties, and was related to noodle texture, flour protein content, protein composition, dough physical properties and other quality predicting tests.Viscoelasticity of heat-treated gluten, isolated with 2% NaCl solution, significantly correlated with most of the tests used to measure dough and/or gluten strength and Chinese white salted noodle texture. The rate of thermal denaturation of proteins depends on M_r and packing density. High ratios of monomeric proteins such as gliadins and low M_r glutenin subunits to high M_r glutenin subunits increase the thermostability of the gluten. The measurement of viscoelasticity of heat-denatured gluten can be a useful test to determine gluten quality. Our study showed that gluten viscoelasticity and most of the tests related to dough and/or gluten strength are independent of allelic variations of the high molecular weight glutenin subunits. This test has been developed for predicting white salted noodle quality.     

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.     

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.     

Proteomic analysis of wheat recombinant inbred lines: Variations in prolamin and dough rheology

To investigate the impact of the 1BL.1RS translocation on dough strength and to understand how 1BL.1RS genotypes may overcome the loss of Glu-B3 and Gli-B1, proteomic profiles of 16 doubled haploid (DH) lines of similar glutenin composition but of different strength, as measured by Chopin's alveograph, were compared. The results showed that 32 spots, mainly prolamins, were differentially expressed and that five others were specific to high-strength DH lines. The identification and quantification of the prolamin fractions on the two-dimensional (2D) electrophoresis gels demonstrated that the high-molecular weight glutenin sub-unit (HMW-GS) were up-regulated by 25% in 1BL.1RS DH lines, even though the corresponding genes were not located on the missing 1BS chromosome. The γ-gliadins were also up-regulated (by 36%) in such lines to counterbalance, to some extent, the loss of LMW-GS of Glu-B3. The polymeric prolamin fractions also accumulated in high-tenacity lines and decreased in high-extensibility lines confirming the role of the inter-chain disulfide bonds in resistance to deformation. In contrast, the monomeric fraction of α-gliadin favored extensibility and decreased tenacity by increasing the accumulation (+12%) of α-gliadins in high-extensibility lines; the Gli-A1 allele of the parent Toronit was found to be more abundant when compared to the Gli-A1 allele of parent 211.12014.     

Detection of y-type Subunit at theGlu-A1Locus in Some Swedish Bread Wheat Lines

Electrophoretic and reversed phase high performance liquid chromatographic (RP–HPLC) analyses were performed on gluten proteins extracted from flours milled from two different Swedish bread wheat lines; these lines have been reported to possess a novel highM_rglutenin subunit controlled by a gene at theGlu-A1locus, referred to as 21*. Although RP–HPLC indicated that subunit 21* has a surface hydrophobocity similar to that of the commonly occurring allelic subunits 1 or 2*, it differs from them in isoelectric point, being more basic when analysed by two dimensional gel electrophoresis (IEF/SDS–PAGE). RP–HPLC separations of highM_rglutenin subunits showed the presence of an additional peak, the behaviour of which was similar to that of y-type subunits encoded by genes at theGlu-A1ylocus and present only in wild wheatsT. urartu(AA) orT. dicoccoides(AABB). Based on chromatographic results and on the tight linkage observed with subunit 21*, it is suggested that the additional component (indicated as 21*y), present in the breeding lines analysed, corresponds to the y-type subunit encoded at theGlu-A1locus. Genes encoding the subunits 21* and 21*y were also analysed by polymerase chain reaction (PCR). Contrary to what was observed for the polypeptide itself, the gene corresponding to subunit 21* was similar in size to that encoding subunit 2* and shorter than that corresponding to subunit 1. Moreover, the amplification product corresponding to the active 21*y gene was shorter than that of the allelic inactive gene present in the bread wheat cultivar Cheyenne. As reported for other highM_rglutenin subunits, gene size differences observed were due to a different length of the repetitive region. Because cultivated polyploid wheats have been shown to have only the x-type subunit at theGlu-A1locus, it is speculated that the new combination, with both x- and y-type subunits expressed, might have been introgressed during breeding processes from the wild wheat progenitorsT. urartuorT. dicoccoides, which have genotypes expressing both types of subunits.     

High frequency of abnormal high molecular weight glutenin alleles in Chinese wheat landraces of the Yangtze-River region

A total of 485 common landraces of bread wheat were collected from the Yangtze-River region of China. Their high molecular weight glutenin subunit (HMW-GS) composition was analyzed by Matrix-assisted laser desorption/ionization time-of-flight Mass Spectrometry (MALDI-TOF-MS). Among all landraces tested, 453 were homogeneous for HMW-GS, 32 were heterogeneous, and 37 contained abnormal subunits. A total of 22 alleles were detected, including 3 at Glu-A1, 13 at Glu-B1 and 6 at Glu-D1, respectively. Higher variations occurred at the Glu-B1 locus compared with Glu-A1 and Glu-D1. Glu-A1c (74.0%), Glu-B1b (40.4%), Glu-D1a (84.9%) appeared to be the most frequent alleles at Glu-A1, Glu-B1 and Glu-D1, respectively. Two alleles ("null" and 1) at the Glu-A1 locus, three allele compositions (7 + 8, 7OE + 8, 7 + 9) at the Glu-B1 locus, and two (2 + 12 and 5 + 10) at the Glu-D1 locus appeared to be the common types in the 485 landraces. Sixteen new alleles represented by abnormal subunits were identified at the Glu-B1 and the Glu-D1 locus.     

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.     

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.     

Preparative Separation of High and Low Molecular Weight Subunits of Glutenin from Wheat

Wheat flour was washed with Tris-HCl buffer containing 4% Triton X114 before extracting the residual gluten with 70% ethanol. The glutenin extraction with 50% ethanol was performed at various ratios of DTT/protein; a minimum ratio of 0·1 g/g was needed to solubilise the maximum amount of glutenin. An experimental design was used to optimise the extraction conditions to obtain the best yield and purity of lowM_rand highM_rglutenin subunits. The purity of each glutenin subunit fraction was measured by RP-HPLC analysis after reduction and alkylation. Both temperature and protein concentration had an effect on the preparation of these fractions. An increase in the protein concentration enhanced the yield of the highM_rglutenin fraction and simultaneously decreased that of the lowM_rglutenin. Using the Deringer desirability function, conditions giving the optimum separation were determined. The procedure was scaled up and permitted the preparation of 0·96 g of highM_rand 1·64 g of lowM_rglutenin subunits from 5 g of gluten. The purities of these fractions, determined by RP-HPLC, were 90% and 95%, respectively, and their amino acid compositions were similar to those of high and lowM_rsubunits separated by RP-HPLC.     

Influence of allelic prolamin variation and localities on durum wheat quality

Thirty-seven varieties of a Mediterranean durum wheat collection grown in Tunisia and Spain were analysed for their allelic composition in prolamins, as well as their protein concentration, sodium dodecyl sulphate sedimentation (SDSS) test and mixograph parameters. Genotype was a greater source of variation in all measurements than locality. Uncommon high and low molecular glutenin subunits (HMW-GS and LMW-GS) were found (V and 2•• subunits at Glu-A1, 13 + 16 at Glu-B1, 5* subunit and ax allele at Glu-A3). The rare combinations 2 + 4+14 + 18 and 8 + 9+13 + 16+18 subunits at the Glu-B3 locus were found. Glu-A3ax had a positive influence on SDSS and mixograph parameters. Of all the prolamins, those that have the B-LMW-GS composition aaa (for Glu-A3, Glu-B3 and Glu-B2 loci, respectively), when associated with the Glu-A1c and Glu-B1d gave the best semolina quality. By contrast, semolina quality is poor when this same composition is associated with the Glu-A1c and Glu-B1e and even poorer when associated with the Glu-A1c and Glu-B1f. In addition, the cultivars with B-LMW-GS allelic composition aab (for Glu-A3, Glu-B3 and Glu-B2 loci, respectively), when associated with the Glu-A1c and Glu-B1d, gave high quality, whereas when associated with the Glu-A1c and Glu-B1e or with Glu-A1o and Glu-B1f, the quality was very poor.     

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.     

普通小麦Glu-3位点基因单元型的分离和序列分析

为了从分子水平上探讨优质小麦资源中LMW-GS等位基因与小麦品质的关系,以及在改善小麦品质方面的潜在价值,利用小麦Glu-A3和Glu-B3基因的特异引物从强筋型、中筋型和弱筋型小麦共计10份材料中分离出LMW-GS基因后进行序列分析。结果表明,共发现14个新的核苷酸变异类型和4个肽链变异类型。其中,14个新的核苷酸变异类型中,4个为Glu-A3基因变异类型,1个为Glu-B3基因变异类型,9个为Glu-D3基因变异类型。值得注意的是,有2个半胱氨酸数目特殊的亚基类型被发现,一个是来自师栾02-1含有9个半胱氨酸残基的GluA3-18基因,另一个是来自偃展4110含有7个半胱氨酸残基的GluD3-13基因。     

Y-type gene specific markers for enhanced discrimination of high-molecular weight glutenin alleles at the Glu-B1 locus in hexaploid wheat

A number of primers were designed which target DNA sequence variation of the coding and /or promoter regions of wheat HMW glutenin y-type genes located at the Glu-B1 locus. This allowed the development of a set of PCR-based markers for specific HMW glutenin genes encoding By-subunits for which no markers were previously available. Markers were validated using test cultivars containing specific Glu-B1 alleles confirmed by SDS-PAGE and RP-HPLC analysis. Among the specific markers developed, primer pair ZSBy8F5/R5 was specific for the By8 gene, which exists in Glu-B1b (Bx7+By8) and Glu-B1u (Bx7*+By8) alleles. This marker allows discrimination of alleles containing By8 and By8* that are usually difficult to distinguish using SDS-PAGE. Since the over-expressed Glu-B1 allele (Glu-Bl al.) contains the By8* subunit, it is possible to use this marker in breeding programs for selecting for the over-expression of subunit Bx7 in crosses that segregate between normal Bx7 and over-expressed Bx7 subunits. This marker also represents an alternative for distinguishing two common Glu-B1 alleles: Glu-B1i (Bx17+By18) and Glu-B1b (Bx7+By8). Two primer pairs ZSBy9aF1/R3 and ZSBy9F7/R6 both gave characteristic banding patterns for Glu-B1c (Bx7+By9) and can therefore be used to discriminate By9 - containing alleles from non - By9 alleles. Primer pair ZSBy9F2/R2 produced amplicons with a diagnostic banding pattern for allele Glu-B1f (Bx13+By16) and also permitted the discrimination of Glu-B1h (Bx14+By15) and Glu-B1e (Bx20) that have opposing genetic effects on wheat quality and are difficult to discriminate by SDS-PAGE.