Development of a kompetitive allele‐specific PCR marker for selection of the mutated Wx‐D1d allele in wheat breeding

Waxy (Wx) protein is a key enzyme for synthesis of amylose in endosperm. Amylose content in wheat grain influences the quality of end‐use products. Seven alleles have been described at the Wx‐D1 locus, but only two of them (Wx‐D1b, Wx‐D1e) were genotyped with codominant markers. The waxy wheat line K107Wx1 developed by treating ‘Kanto 107’ seeds with ethyl methanesulphonate carries the Wx‐D1d allele. However, no molecular basis supports this nomenclature. In the present study, DNA sequence analysis confirmed that a single nucleotide polymorphism in the sixth exon of Wx‐D1 changed tryptophan at position 301 into a termination codon. Based on this sequence variation, a PCR‐based KASP marker was developed to detect this point mutation using 68 BC₈F₁ plants and 297 BC₈F₂ lines derived from the cross ‘Ningmai 14’*9/K107Wx1. Combined with codominant markers for the Wx‐A1 and Wx‐B1 alleles, waxy and non‐waxy near‐isogenic lines were distinguished. The KASP marker was efficient in identifying the mutant allele and can be used to transfer waxiness to elite lines.     

Introduction of high molecular weight glutenin subunits 5 + 10 for the improvement of the bread-making quality of hexaploid triticale

In an earlier study, chromosome 1D of the hexaploid breadwheat cultivar ‘Chinese Spring’ was introduced into hexaploid triticale to improve its bread‐making quality. That specific chromosome, 1D, carried the a allele at the Glu‐D1 locus coding for high molecular weight (HMW) glutenin subunits 2 + 12, and since subunits 2 + 12 are associated with poor bread‐making quality in wheat, in the present study hexaploid 1D substitution triticale was crossed with octoploid triticale with the d allele at the Glu‐D1 locus encoding HMW glutenin subunits 5 + 10. Following backcrosses to different triticale varieties, 1D substitution lines were established that had Glu‐D1 allele a or d in an otherwise genetically similar background, and the influence of these two different alleles on bread‐making quality of hexaploid triticale was compared. The agronomic performance of 76 selected lines was evaluated in a field trial. The Zeleny sedimentation value was determined as a parameter for bread‐making quality, and related to the presence of chromosome 1D, the different glutenin alleles and the nature of the substitution. The presence of chromosome 1D had a significant and positive effect on the Zeleny sedimentation value, but the difference between the two glutenin alleles 2 + 12 and 5 + 10 was not as obvious as in wheat. Owing to its high cytological stability and minimal effect on agronomic performance, substitution 1D(1A) appears to be the most desirable one to use in triticale breeding.     

Detection of HMW glutenin subunit variations among 205 cultivated emmer accessions (Triticum turgidum ssp. dicoccum)

The high molecular weight glutenin subunits (HMW‐GS) encoded by Glu‐1 loci among 205 accessions of cultivated emmer wheat (Triticum turgidum ssp. dicoccum Schrank) collected from different regions of Europe and China were separated and characterized by SDS‐PAGE in combination with two‐dimensional gel electrophoresis (A‐PAGE × SDS‐PAGE) and acidic capillary electrophoresis. High genetic polymorphisms in HMW‐GS compositions were found. A total of 40 alleles (6 for Glu‐A1 and 34 for Glu‐B1) and 62 subunit combinations (genotypes) were detected, some of which were not previously described. At Glu‐A1 locus, two novel alleles, designated Glu‐A1x coding for the subunit 1A × 1.1 and Glu‐A1y coding for the subunit 1A × 2.1′ were found while seven new subunits (1B × 17*, 1B × 6′, 1B × 13′, 1B × 20*, 1By9*, 1By14.1 and 1By8.1) and 20 novel alleles at Glu‐B1 locus were detected. In particular, some additional protein components were detected, which probably were 1Ay subunits encoded by Glu‐A1 locus. The introduction of both Ax and Ay subunits from tetraploid wheats into hexaploid wheats may increase the genetic variability of gluten genes and consequently improve flour technological properties.     

Positive effect of the high-molecular-weight glutenin allele, Glu-D1d, on the bread-making quality of common wheat

The seed storage proteins of wheat flour are the determinants of bread‐making quality. Many cultivars having good bread‐making quality carry the Glu‐D1d allele responsible for the development of glutenin, a major seed storage protein. The Glu‐D1d allele was introduced into four leading Japanese wheat cultivars by recurrent backcrossing and the quality of these near‐isogenic lines (NILs) was evaluated by the sodium dodecyl sulphate sedimentation value of their flour. The values for the NILs were significantly higher than for the corresponding recipient cultivars. However, the values did not reach the level of the cultivar that had been used as the donor of the Glu‐D1d allele.     

Evaluation of cold hardiness in two sets of near-isogenic lines of wheat (Triticum aestivum) with polymorphic vernalization alleles

In wheat, variation at the orthologus Vrn‐1 loci, located on each of the three genomes, A, B and D, is responsible for vernalization response. A dominant Vrn‐1a allele on any of the three wheat genomes results in spring habit and the presence of recessive Vrn‐1b alleles on all three genomes results in winter habit. Two sets of near‐isogenic lines (NILs) were evaluated for DNA polymorphisms at their Vrn‐A1, B1 and D1 loci and for cold hardiness. Two winter wheat cultivars, ‘Daws’ and ‘Wanser’ were used as recurrent parents and ‘Triple Dirk’ NILs were used as donor parents for orthologous Vrn‐1 alleles. The NILs were analysed using molecular markers specific for each allele. Only 26 of 32 ‘Daws’ NILs and 23 of 32 ‘Wanser’ NILs had a plant growth habit that corresponded to the marker genotype for the markers used. Freezing tests were conducted in growth chambers programmed to cool to ?21.5°C. Relative area under the death progress curve (AUDPC), with a maximum value of 100 was used as a measure of death due to freezing. The average relative AUDPC of the spring habit ‘Daws’Vrn‐A1a NILs was 86.15; significantly greater than the corresponding winter habit ‘Daws’Vrn‐A1b NILs (42.98). In contrast, all the ‘Daws’Vrn‐A1bVrn‐B1aVrn‐D1b and Vrn‐A1bVrn‐B1bVrn‐D1a NILs (spring habit) had relative AUDPC values equal to those of their ‘Daws’ sister genotypes with Vrn‐A1bVrn‐B1bVrn‐D1b NILs (winter habit). The average AUDPC of spring and winter habit ‘Wanser’ NILs differed at all three Vrn‐A1, Vrn‐B1 and Vrn‐D1 locus comparisons. We conclude that ‘Daws’ and ‘Wanser’ have different background genetic interactions with the Vrn‐1 loci influencing cold hardiness. The marker for Vrn‐A1 is diagnostic for growth habit and cold hardiness but there is no relationship between the Vrn‐B1 and Vrn‐D1 markers and the cold tolerance of the NILs used in this study.     

Characterization of CIMMYT bread wheats for high- and low-molecular weight glutenin subunits and other quality-related genes with SDS-PAGE,RP-HPLC and molecular markers

Two hundred and seventy-three CIMMYT bread wheat cultivars and advanced lines grown under irrigated conditions in Mexico during the 2005-06 Yaqui crop cycle were characterized for quality-related genetic traits using gene-specific markers for some high- and low-molecular-weight glutenin subunit (HMW-GS and LMW-GS) genes, polyphenol oxidase (PPO), phytoene synthase (PSY), and waxy genes. Of them, 142 were analyzed for quality parameters including SDS sedimentation volume (SDS-SV), dough mixing time, and Alveograph parameters, and for HMW-GS and LMW-GS compositions using sodium-dodecyl-sulfate polyacrylamide gel electrophoresis (SDS-PAGE), and reversed-phase high-performance liquid chromatography (RP-HPLC). For the Ppo-A1 locus tested with the marker PPO18, the frequencies of alleles Ppo-A1a and Ppo-A1b were 79.1 and 20.2%, respectively, and no PCR fragment was amplified in 2 lines (0.73%), whereas 227 lines (83.2%) contained the allele Ppo-D1a and 46 lines (16.8%) had Ppo-D1b detected by markers PPO16 and PPO29. For the marker YP7A, 142 lines (52.0%) were assumed to have the allele Psy-A1a and 131 lines (48.0%) contained the allele Psy-A1b. In the case of the marker YP7B for the gene Psy-B1, the alleles Psy-B1a and Psy-B1b were detected in 155 (56.8%) and 43 (15.8%) lines, respectively, and 75 (27.4%) lines possessed the allele Psy-B1d detected by the marker YP7B-3. All 273 lines contained the alleles Wx-A1a and Wx-D1a as determined by markers MAG264 and MAG269, respectively. Using the marker Wx-B1, 204 lines (74.7%) were presumed to have the Wx-B1a allele and 69 (25.3%) possessed Wx-B1b. The over-expressing allele of Bx7 ^OE and subunit By8*, not clearly seen with SDS-PAGE, were detected by RP-HPLC. The numbers of lines with subunits Ax2*, By8, By9, Bx17, Bx20, Dx5, and Glu-B3j were 90, 16, 57, 5, 46, 118, and 33, respectively, in the 142 lines analyzed with molecular markers, and were consistent with the results obtained by SDS-PAGE, except for one line with the 1A.1R translocation. Subunits Ax1 and Ax2* at the Glu-A1 locus showed significantly better effects on all quality parameters than subunit Null. Subunits 5 + 10 gave significantly better effects for all parameters. Subunit Glu-A3b showed more positive effects than its alternative alleles on SDS-SV and SDS-sedimentation volume/protein content index (SPI). The allele Glu-B3g showed the best effect on SDS-SV and Alveograph W, whereas Glu-B3j, associated with the 1B.1R translocation, exhibited a strongly negative effect on all quality parameters.     

Survey and new insights in the application of PCR‐based molecular markers for identification of HMW‐GS at the Glu‐B1 locus in durum and bread wheat

Wheat, among all cereal grains, possesses unique characteristics conferred by gluten; in particular, high molecular weight glutenin subunits (HMW‐GS) are of considerable interest as they strictly relate to bread‐making quality and contribute to strengthening and stabilizing dough. Thus, the identification of allelic composition, in particular at the Glu‐B1 locus, is very important to wheat quality improvement. Several PCR‐based molecular markers to tag‐specific HMW glutenin genes encoding Bx and By subunits have been developed in recent years. This study provides a survey of the molecular markers developed for the HMW‐GS at the Glu‐B1 locus. In addition, a selection of molecular markers was tested on 31 durum and bread wheat cultivars containing the By8, By16, By9, Bx17, Bx6, Bx14 and Bx17 Glu‐B1 alleles, and a new assignation was defined for the ZSBy9_aF1/R3 molecular marker that was specific for the By20 allele. We believe the results constitute a practical guide for results that might be achieved by these molecular markers on populations and cultivars with high variability at the Glu‐B1 locus.     

Development of AS‐PCR marker based on a key mutation confirmed by resequencing of Wx‐mp in Milky Princess and its application in japonica soft rice (Oryza sativa L.) breeding

Soft rice with low amylose content (AC) ranging by 5–15% is a unique type with special eating and appearance quality and has become popular in the rice market. We resequenced the Wx‐mp, a key allele from Milky Princess, a Japanese low AC variety, and found that the +473 mutation in exon 4 is the key mutation in both Wx‐mp and its ancestor allele, Wx‐mq from Milky Queen. Based on this functional mutation, an allele‐specific PCR (AS‐PCR) marker was developed and proven in a breeding population derived from a cross between a Chinese late variety Nan Keng 46 (Wx‐mp/Wx‐mp) and an early line Ning 63121(Wx‐b/Wx‐b). Based on the marker‐aided selection by our newly developed AS‐PCR marker for Wx‐mp and the known ST10 marker for Stvb‐i, a total of 12 Wx‐mp homozygotes were selected from 198 F₂ progenies, and four of them were immune to rice stripe virus (RSV) with averagely 11.3 days earlier heading than Nan Keng 46 without significant change in grain yield.     

Waxy proteins in diploid, tetraploid and hexaploid wheats

Electrophoretic analyses of waxy proteins, encoded by genes present at the Wx‐1 loci, present in several cultivars and accessions of hexaploid wheat, Triticum aestivum, have permitted the detection of null alleles at the Wx‐B1 and Wx‐D1 loci. Polymorphism at the Wx‐A1 and Wx‐B1 loci was also investigated in several accessions of tetraploid wheats, Triticum durum, Triticum dicoccoides and Triticum timopheevi, and in diploid species, Triticum urartu, Triticum boeoticum and Triticum monococcum. One null allele at the Wx‐A1 locus and three polymorphic alleles at Wx‐B1 locus were detected in T. durum; a new allele at one of the two waxy loci was identified in the tetraploid wheat T. timopheevi; no polymorphism was detected in diploid species. Polymerase chain reaction techniques made possible the detection of further polymorphism existing at the Wx‐1 loci and the reason for the lack of expression of the null genotypes to be investigated. The null forms detected at each locus have been used to produce complete sets of partial and total waxy lines in durum and bread wheat.     

Detection of QTLs for bread‐making quality in wheat using a recombinant inbred line population

Whereas gluten fraction accounts for 30–60% of the variation in wheat bread‐making quality, there remains substantial variation determined by non‐gluten factors. The objective of this study was to detect new loci for wheat quality. The genetics of sodium dodecyl sulphate‐sedimentation volume (Ssd), grain hardness (GH), grain protein content, wet gluten content (WGC) and water absorption (Abs) in a set of 198 recombinant inbred lines derived from two commercial varieties was studied by quantitative trait loci (QTL) analysis. A genetic map based on 255 marker loci, consisting of 250 simple sequence repeat markers and five glutenin loci, Glu‐A1, Glu‐B1, Glu‐D1, Glu‐B3 and Glu‐D3, was constructed. A total of 73 QTLs were detected for all traits. A major QTL for GH was detected on chromosome 1B and its relative contribution to phenotypic variation was 27.7%. A major QTL for Abs on chromosome 5D explained more than 30% of the phenotypic variation. Variations in Ssd were explained by four kinds of genes. Some QTLs for correlated traits mapped to the same regions forming QTL clusters or indicated pleiotropic effects.     

Segregation for isozymes and HMW glutenins in a doubled-haploid cross of winter wheat carrying 1BL.1RS and 5DL.5RS translocations from rye

The doubled haploid (DH) wheat line ‘dh 5841’ carrying two translocations from rye, 5DL.5RS and 1BL.1RS, has been crossed to the subline of wheat cultivar ‘Amadeus 7143’ with a 1BL.1RS translocation. The resulting F₁ hybrid IJ 98 with a heterozygous 5DL.5DS‐5DL.5RS chromosome pair has been used to produce doubled haploids. A total of 57 DH lines were obtained from plantlets regenerated in anther culture after successful colchicine treatment and seed set. These lines were identified regarding the constitution of chromosome 5D (5DL.5DS or 5DL.5RS) by means of isoenzyme marker analysis. Thirty DH lines possessed the 5DL.5DS chromosome, while the remaining 27 lines carried the 5DL.5RS translocation. For some of these lines, the 5DL.5RS chromosome was cytologically confirmed by C‐banding. Furthermore, the DH lines were evaluated for their high molecular weight glutenin subunit composition. All possible combinations for the four independent loci —Skdh, Glu‐Al, Glu‐B1 and Glu‐D1— were detected in only 57 DH lines and no segregation distortion was observed.     

Influence of allelic variations in glutenin on the quality of pan bread and white salted noodles made from Korean wheat cultivars

Dough rheological properties and end-use quality were evaluated to determine the effects of Glu-1 and Glu-3 alleles on those characteristics in Korean wheat cultivars. SDS-sedimentation volume based on protein weight was positively correlated with mixograph parameters and maximum height of dough and also positively correlated with bread volume, crumb firmness and springiness of cooked noodles. Protein content was negatively correlated with optimum water absorption of noodle dough, lightness of noodle dough sheet and hardness and cohesiveness of cooked noodles. Within Glu-1 loci, 1 or 2* subunit and 5 + 10 subunits showed longer mixing time, higher maximum dough height and larger bread volume than other alleles. Cultivars with 13 + 16 subunits at Glu-B1 locus showed higher protein content and optimum water absorption of mixograph than cultivars with 7 + 8 subunits. At Glu-3 loci, Glu-A3d showed longer mixing time than Glu-A3e, and Glu-B3d and Glu-B3h had stronger mixing properties than Glu-B3i. Glu-B3h had higher bread volume and hardness of cooked noodles than Glu-B3d. Glu-D3a had lower protein content than Glu-D3c, and Glu-D3b showed stronger mixing properties than Glu-D3a. Glu-D3c showed lower hardness of cooked noodles than others.     

The high and low molecular weight glutenin subunit polymorphism of Algerian durum wheat landraces and old cultivars

The high molecular weight (HMW) and B‐zone low molecular weight (B‐LMW) glutenin subunit composition of 45 Algerian durum wheat (Triticum turgidum L. var. durum) landraces and old cultivars were examined by sodium‐dodecyl‐sulphate polyacrylamide gel electrophoresis (SDS‐PAGE). Nine accessions were heterogeneous and presented two or three genotypes. All together, 33 glutenin patterns were detected, including 12 for HMW and 15 for B‐LMW glutenin subunits. Twenty‐four different alleles were identified for the five glutenin loci studied, Glu‐A1 (3), Glu‐B1 (6), Glu‐A3 (8), Glu‐B3 (5) and Glu‐B2 (2). Five new alleles were found, three at Glu‐A3 and two at Glu‐B3. At the Glu‐1 loci, the Glu‐A1c‐Glu‐B1e allelic composition was predominant (31%). For the B‐LMW glutenins, the most common allelic composition was Glu‐A3a‐Glu‐B3a‐Glu‐B2a (36%). The collection analysed shows a high percentage of glutenin alleles and allele combinations related to high gluten strength, together with some others that have not been tested so far. This information could be useful to select local varieties with improved quality and also as a source of genes to develop new lines when breeding for quality.     

Waxy proteins and amylose content in diploid Triticeae species with genomes A, S and D

A collection of 89 accessions of diploid species of wheat was analysed for waxy protein in the grain: 39 accessions of Einkorn wheats, 41 accessions of Sitopsis section wheat and nine accessions of Triticum tauschii. The electrophoretic patterns showed low polymorphism. In each group of wheat, a single and different allele was detected. In accessions of Einkorn wheats that allele had a similar electrophoretical mobility to the Wx‐A1a allele of the bread wheat ‘Chinese Spring’, in accessions of the Sitopsis section it had a similar mobility to that of the Wx‐B1f allele of tetraploid wheat, and in the accessions of T. tauschii, it was similar to the Wx‐D1a allele of the bread wheat ‘Chinese Spring’. The accessions were also analysed for apparent amylose content. Results showed that amylose content ranged from 22 to 35% in Einkorn wheats, from 28 to 41% in the Sitopsis section and from 26 to 35% in accessions of T. tauschii.     

小麦优质谷蛋白亚基分子标记多重PCR体系的建立与应用

Ax1/Ax2*、Dx5和过量表达的Bx7亚基(Bx7^OE)被认为是对小麦品质有正向效应的优质亚基。根据以上亚基特异性分子标记建立相应的多重PCR体系,经品种和群体检验,证明利用该体系鉴定亚基的结果稳定可靠、成本较低。利用该多重PCR技术对89份西藏小麦育成和推广品种(系)的优质亚基频率进行鉴定,结果表明, Dx5和Ax1/Ax2*亚基的频率均为12.4%,没有检测到Bx7^OE,同时携带两个优质亚基的材料频率为10.1%,该麦区品质育种必须加强优质亚基的引入。针对优质亚基Ax1/Ax2*、Dx5和Bx7^OE的多重PCR体系,为小麦品质育种亲本评价和通过杂交方法聚合优质亚基基因提供了一种实用可靠的标记辅助选择技术。     

Genetic and Molecular Characterization of Vernalization Genes Vrn‐A1, Vrn‐B1, and Vrn‐D1 in Spring Wheat Germplasm from the Pacific Northwest Region of the U.S.A.

The objective of this study was to determine the Vrn‐1 allelic composition of spring wheat germplasm from the Pacific Northwest region of the USA. Individual plants from 56 spring wheat lines were crossed to near‐isogenic tester lines carrying the dominant allele Vrn‐A1, Vrn‐B1 or Vrn‐D1. F₂ progeny were evaluated for growth habit in the field and Vrn‐1 allelic composition was determined through chi‐square analysis. Lines also were analysed with DNA sequence‐based Vrn‐1 allele‐specific markers. A majority of the germplasm carried the dominant allele Vrn‐A1a alone or in combination with Vrn‐B1, Vrn‐D1 or Vrn‐B3 alleles. Vrn‐B1 and Vrn‐D1 were almost always associated with other dominant Vrn‐1 allele(s). Based on DNA sequence analysis, a novel Vrn‐B1 allele referred to as Vrn‐B1b, which carried a single nucleotide polymorphism (SNP) and a 36 bp deletion, was identified in cultivar ‘Alpowa’. These results will be useful to wheat breeders for choosing parents with different Vrn‐1 alleles for crossing to maximize diversity at the Vrn‐1 loci with an expectation of identifying superior Vrn‐1 allelic combinations for cultivar improvement.     

Glutenin allelic variation and 1AL.1RS effects on dough mixing properties of wheat grown in irrigated and rainfed environments

Wheat (Triticum aestivum L.) glutenin allelic variation and presence of the 1AL.1RS wheat-rye (Secale cereale L.) translocation play important roles in determining end-use quality. This study was conducted to evaluate the effects of high and low molecular weight glutenin alleles and 1AL.1RS on dough mixing properties of 189 recombinant inbred lines (RILs) from the cross TAM 107-R7/‘Arlin’ grown in irrigated and rainfed Colorado (USA) environments. The results indicated that (1) higher values (P < 0.05) of some dough mixing properties were observed for Glu-A1b versus Glu-A1a, Glu-B1b versus Glu-B1c, Glu-D1d versus Glu-D1a, and non-1AL.1RS versus 1AL.1RS; (2) no differences in Mixograph properties were found for Glu-A3c versus Glu-A3e, Glu-B3e versus Glu-B3g, or Glu-D3a versus Glu-D3b; (3) although variation at some glutenin loci had little effect on Mixograph properties, pairwise combinations of glutenin loci or a glutenin locus combined with 1AL.1RS affected most Mixograph traits; and (4) in general, the effects of glutenin alleles and 1AL.1RS on dough mixing properties did not differ greatly between the irrigated and the rainfed environment. These results will be useful for assessing potential wheat quality and directing wheat breeding efforts in Colorado and similar environments.     

Effect of VRN‐1 and PPD‐D1 genes on heading time in European bread wheat cultivars

The variation of the vernalization (VRN‐1) and photoperiod (PPD‐1) genes offers opportunities to adjust heading time and to maximize yield in crop species. The effect of these genes on heading time was studied based on a set of 245 predominantly spring cultivars of bread wheat from the main eco‐geographical regions of Europe. The genotypes were screened using previously published diagnostic molecular markers for detecting the dominant or recessive alleles of the major VRN‐1 loci such as: VRN‐A1, VRN‐B1, VRN‐D1 as well as PPD‐D1. We found that 91% of spring wheat cultivars contain the photoperiod sensitive PPD‐D1b allele. Photoperiod insensitive PPD‐D1a allele has been found mainly in southern region of Europe. For this region the monogenic control of vernalization by VRN‐B1 or VRN‐D1 dominant alleles is common, whereas in the remaining part of Europe, the combination of photoperiod sensitive PPD‐D1b allele with dominant VRN‐A1, VRN‐B1 and recessive vrn‐D1 alleles represents the most frequent genotype. Also, we revealed a significantly later (5–8 days) heading of the monogenically dominant genotypes at VRN‐B1 as compared to the digenic VRN‐A1 VRN‐B1 genotypes.     

Diversity of five glutenin loci within durum wheat (Triticum turgidum L. ssp. durum (Desf.) Husn.) germplasm grown in Algeria

The HMW and B‐LMW glutenin subunits composition of 120 durum wheat germplasm grown in Algeria was examined using SDS‐PAGE. All together, 39 glutenin patterns were detected, including eight for HMW and 21 for B‐LMW glutenin subunits. Twenty‐six different alleles were identified for the five glutenin loci studied, that is, Glu‐A1 (3), Glu‐B1 (7), Glu‐A3 (5), Glu‐B3 (9) and Glu‐B2 (2). Two new alleles were found at Glu‐B3 locus: Glu‐B3new₁ encodes for five subunits (7 + 8 + 14 + 16 + 18) and Glu‐B3new₂ codes for five subunits (4 + 6* + 12 + 15 + 15*), of which subunit 15* with mobility between bands 15–16 was not described previously. At the Glu‐1 loci, the Glu‐A1c/Glu‐B1e allelic composition was predominant. For the B‐LMW glutenins, the most common allelic composition was Glu‐A3a/Glu‐B3a/Glu‐B2a. The collection analysed shows glutenin alleles and allele combinations related to high gluten strength. This information could be useful to select varieties with improved quality and also as a source of genes to develop new lines when breeding for quality.     

2··, a new high molecular weight glutenin subunit coded by Glu-A1: its predicted structure and its impact on bread-making quality

The suitability of wheat varieties for bread‐making depends on their glutenin subunits. The amino acid composition of these gluten building‐blocks have a strong influence on the rheology of the dough and, thus, on the suitability of the variety for bread‐making. This study reports a new x‐type high molecular weight glutenin subunit coded by the locus Glu‐A1 and named 2··. To investigate the impact of this allele on 10 quality parameters, a doubled haploid (DH) population of Triticum aestivum, segregating for Glu‐A1, was created. The statistical analysis demonstrates that, at Glu‐A1, the subunit 2·· is as favourable for quality as the subunit 2*. This is in accordance with results showing that the 2·· open reading frame still has the same number of cysteines as 2*. The small differences in the length of the central domain had no detectable effect on the elasticity, tenacity and baking quality, of the dough.