High molecular weight glutenin subunit composition of Chinese bread wheats

Summary The endosperm storage proteins of 205 Chinese bread wheat cultivars and advanced lines were fractionated by SDS-PAGE to determine their high molecular weight (HMW) glutenin subunit composition. Seventeen alleles were identified: three at Glu-A1, eight at Glu-B1, and six at Glu-D1. The most common alleles were Null, 1, 7+8, 7+9, and 2+12. The results indicate that wheats from different regions differ in their frequencies of HMW glutenin subunits, however, none of the subunits could be related to specific environments. The glutenin quality scores of Chinese wheats ranged from 3 to 10, with an average of 6.7. Increasing quality scores have implications in improving steam-bread making quality for Chinese consumers. On the basis of HMW glutenin subunit composition, Chinese wheats are close to European wheats, especially Italian wheats because several Italian introductions are widely distributed in the pedigrees of Chinese wheat.     

The high and low molecular weight glutenin subunits and ω-gliadin composition of bread and durum wheats commonly grown in Portugal

A collection of 63 bread wheats (Triticum aestivum L.) and 21 durum wheats (Triticum durum Desf.) commonly grown in Portugal since 1982 were characterized for the composition of wheat storage proteins (WSP), high molecular weight glutenin subunits (HMW-GS), low molecular weight glutenin subunits (LMW-GS) and ω-gliadins. The composition of HMW-GS, LMW-GS and &-gliadins, encoded at loci Glu-1, Glu-3 and Gli-1, respectively, was revealed by sodium dodecyl sulphate polyacrylamide gel electrophoresis. WSP allelic compositions of bread and durum wheat patterns were given. In the bread wheats, a total of 24, 24 and 18 patterns were observed for HMW-GS, LMW-GS and ω-gliadins, respectively. Forty-two different alleles were identified for the nine loci studied, Glu-A1 (3), Glu-B1 (7), Glu-D1 (4), Glu-A3 (5), Glu-B1 (7), Glu-D3 (2), Gli-A1 (2), Gli-B1 (8) and Gli-D1 (4). In the case of durum wheats, 19 alleles were identified: one allele at Glu-A1, two at Glu-B3, Glu-B2 and Gli-A1, three at Glu-B1, four at Glu-A3 and five at Gli-B1. For HMW-GS, LMW-GS and ω-gliadins, three, six and six different patterns were revealed, respectively. This study represents the first attempt to discriminate the bread and durum wheat varieties commonly grown in Portugal by the allelic variation of storage proteins. The database is useful for varietal identification and for plant breeders who seek to devise effective programmes aimed at improving wheat quality.     

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.     

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.     

Bread-making quality and yield performance of 1BL/1RS wheat isogenic lines

Isogenic lines were developed in order to assess the precise effects of the 1BL/1RS translocation on quality characteristics and agronomic traits. Results showed that the translocation has a detrimental effect on sodium dodecyl sulphate sedimentation volume, in any background. Yield was similar between translocated and non-translocated lines; however, lines carrying lBL/1RS showed a significant increase in grain weight, together with a decrease in spike number per plant.     

Additive and epistatic effects of allelic variation at the high molecular weight glutenin subunit loci in determining the bread-making quality of breeding lines of wheat

Summary The relation has been studied between the high molecular weight glutenin (HMWg) subunit alleles and the bread-making quality of 226 lines of winter wheat (T. aestivum L.), grown in The Netherlands. The lines represented a wide range of genetic backgrounds, and had not been selected for quality, in contrast to the established varieties used by other authors.The variation in HMWg subunit genotypes accounted for about 20% of the total variation in loaf volume among the lines. Most important was the allelic variation at the Glu-D1 locus. The Glu-D1 allele encoding the subunits 5+10 was superior to its allelic counterpart, encoding 2+12. The difference in average of loaf volume between groups of lines containing 5+10 or 2+12 was negatively related with protein content of the flours. When protein content was below 9.2%, no effect of allelic variation at the Glu-D1 locus was present. Epistatic effects between the Glu-I loci also contributed to the variation in loaf volume of the lines: i.e. the effect of allelic variation at Glu-A1 and Glu-B1 depended on the allele present at the Glu-D1. The contribution of the epistatic effects was about half the contribution of the additive effects, and should therefore be included in predictive models for bread-making quality.     

Effect of the leaf rust resistance gene Lr28 on grain yield and bread-making quality of wheat

Near‐isogenic lines carrying the Lr28 gene developed in five genetic backgrounds were tested for 2 years with and without fungicide treatment. The Lr28 gene increased grain yield, 1000‐grain weight and number of effective tillers per plant under heavy leaf rust infection with no negative effects on yield and bread‐making quality in rust‐free plots. Although a reduction in dough development time was found to be associated with Lr28, it can still be used extensively in wheat breeding programmes.     

High molecular weight glutenin subunits of current bread wheats grown in Iran

Variation of high molecular weight gluteninsubunits (HMW-GS) at the Glu-1 lociwas studied using SDS-PAGE method in 43advanced lines or cultivars commonly grownin Iran. Fourteen alleles and 21 alleliccompositions were detected. Among the 43bread wheats analysed only five showed aunique HMW-GS composition. The mostfrequent HMW-GS patterns were 2^*, 7+8,2+12 and 2^*, 17+18, 2+12 which wereobserved in 13 and six cultivars,respectively. In the remainings, each twoto three lines or cultivars showed a commonHMW-GS pattern. Therefore, allelicvariation at Glu-1 loci is of limitedvalue for cultivar identification comparedwith loci controlling gliadins. Sevencultivars were observed to consist of twoto three biotypes with different alleles.In cultivar Mahdavi a biotype showedinactivity at the Glu-B1 locus. Analready reported rare subunit pair'2^***+12' at Glu-D1locus was found in cultivar Kavir. Theresults of scoring cultivars for theirquality based on the HMW-GS compositionswith an average score of eight, wasgenerally good. Cultivars Inia, Tajan, andadvanced lines N-75-11 and N-75-15 showedquality score equal to 10, whereas Alamootand C-75-5 showed quality scores equal tofive. The quality of former and latterlines and cultivars were considered highestand lowest, respectively. The resultsobtained in this study are useful inbreeding programs to improve bread makingquality, developing uniformity andimproving heterogeneous cultivars by meansof selection of the best genotypes.     

The effect ofGlu-B1 high molecular weight glutenin subunits on biscuit-making quality of wheat

Summary The aim of this study was to assess the effect of specificGlu-B1 HMW-GS on biscuit-making quality. Three soft spring wheat cultivars with the sameGlu-A1 andGlu-D1 HMW-GS, but differentGlu-B1 HMW-GS were used in crosses. F₂₄ derived lines were developed from these crosses.Glu-B1 HMW-GS 6+8 and 17+18; and 7+9 and 17+18 were compared. Lines with HMW-GS 6+8 versus those with HMW-GS 17+18 had a higher flour protein- and alveograph P/L ratio, shorter mixograph mixing time, more vitreous kernels, and a lower alveograph distensibility and strength (all values significant at p=0.05). Lines with HMW-GS 7+9 compared to those with 17+18 showed significant differences for flour extraction and biscuit diameter. The presence of HMW-GS 17+18 was significantly correlated with several biscuit-making quality characteristics in the Dirkwin/Zaragosa F₂₄ lines but not in the Waverley/Zaragosa F₂₄ lines, therefore the effect of HMW-GS 17+18 was modified by the genetic background in which they were expressed.     

Generation and characterization of a high molecular weight glutenin 1Bx14-deficient mutant in common wheat

Significant progress has been made in understanding the structure of high molecular weight (HMW) glutenin subunits and their role in determining the end use quality of wheat grains. However, few reports have dealt with the development and characterization of knock out mutants for HMW glutenin subunit genes. Here, the molecular analysis of MB14, a mutant derived from an elite Chinese wheat variety Xiaoyan 54 through chemical mutagenesis is described. SDS‐PAGE and Western blot experiments revealed that, in the seeds of homozygous MB14 plants, the expression of the 1Bx14 subunit was specifically blocked whereas the remaining four subunits (1Ax1, 1By15, 1Dx2, 1Dy12) accumulated to levels comparable to those in the wild type plants. The 5′‐flanking region and the open reading frame (ORF) of the mutant 1Bx14 allele were amplified and compared to the corresponding regions of wild type 1Bx14. The nucleotide sequences of the 5′‐flanking regions from the mutant and wild type 1Bx14 alleles were identical. However, the ORF of the mutant allele differed from that of the wild type 1Bx14 by three point substitutions, one of which resulted in a premature stop codon in the mutant ORF. Interestingly, the mutant 1Bx14 allele was still transcribed in the developing seeds, but no truncated translation product could be detected by Western blot analysis. Potential application of the 1Bx14 knock out mutant in studying the biological function of 1Bx14 and its contribution to the end use quality control in hexaploid wheat is discussed.     

Agronomic and quality characters of near-isogenic lines of wheat carrying genes for stem rust resistance

Summary Two sets of near-isogenic lines of wheat carrying single genes for stem rust resistance were grown in yield tests to determine whether the resistance genes were deleterious. One set was based on the cultivar Marquis and the second set on a susceptible, day-length insensitive line, LMPG. The results indicated that the effects of resistance genes vary with different genes and different environments. However, there appeared to be a tendency for resistance genes to reduce yield. In most cases the reductions were too small to be of much concern to wheat breeders.     

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.     

Allelic variation and genetic diversity of high molecular weight glutenin subunit in Chinese endemic wheats (Triticum aestivum L.)

The high molecular weight glutenin subunit (HMW-GS) compositions of 66 Chinese endemic wheats were determined by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE). Ten alleles at the Glu-1 loci were detected in 50 Tibetan weedrace wheat accessions which in combination resulted in seven different HMW-GS patterns. Four HMW-GS patterns were observed among 10 Yunnan hulled wheat accessions, and two patterns in six Xingjiang rice wheat accessions. Two novel alleles (Bx7** + By8, Bx7 + By8**) and two rare alleles (Dx2 + 1Dy12*, Dx2 + null) were found in Tibetan weedrace accessions, with one of the latter (Dx2 + Dy12*) also being found in Yunnan hulled wheat. The mean indices of genetic variation at the Glu-1 loci in Yunnan hulled wheat, Tibetan weedrace wheat and Xingjiang rice wheat were 0.2232, 0.1655 and 0.0926, respectively, showing that Yunnan hulled wheat and Tibetan weedrace wheat had higher genetic variation than Xingjiang rice wheat.     

Deficiency of individual high molecular weight glutenin subunits affords flexibility in breeding strategies for bread-making quality in wheat Triticum aestivum L.

High-molecular-weight (HMW) glutenin subunits in wheat Triticumaestivum L., allelic variation for which affects bread-making quality, areencoded by Glu-1 homoeoloci located on the homoeologous group1 chromosomes. Many alleles at Glu-B1 and Glu-D1 producetwo subunits, an x-type of low electrophoretic mobility in polyacrylamidegels, and a y-type of high mobility. In the current study, a combination ofnear isogenic lines of cultivar `Sicco' has been used to characterise theeffect upon quality of the absence of individual subunits 7 (Glu-B1x-type), 12 (Glu-D1 y-type) and, assuming an additive model ofsubunit action, 2 (Glu-D1 x-type). Absence of subunit 7 gave amoderate reduction in SDS-sedimentation volume, indicating its associationwith lower gluten strength (confirmed by Farinogram and Extensogramstudies), yet, from a full mixing input bake, a moderate increase in loafvolume and a considerable improvement in loaf score (an overall evaluationof loaf quality). Absence of subunit 12 gave a slightly larger reduction inSDS-volume, yet no change in loaf volume or score. Absence of bothsubunits 2+12 gave a larger reduction again in SDS-volume, a moderatereduction in loaf volume and a large reduction in loaf score. Absence ofsubunit 2 alone is therefore predicted to reduce SDS-volume, loaf volumeand score such that loss of this x-type subunit would lead to larger changesin quality parameters than loss of y-type subunit 12. A general conclusionof the study is that, while deficiency for HMW glutenin subunits generallyleads to reduced gluten strength and viscoelasticity, the resultantintermediate gluten strength may on occasions lead to improvements in loafperformance in situations where the base gluten strength is high. Theremay, then, be contexts in breeding programmes where selection fordeficiency would be a possible strategy for improving bread-making quality,adding to the flexibility available to the breeder. Somewhat unexpectedly,additional analysis found that, in the genetic background of cultivar `Sicco'used in this study, subunits 7+8 at Glu-B1 were indistinguishablefrom their allelic counterparts subunits 7+9 for virtually all characters, andthat subunits 2+12 at Glu-D1, while inferior in performance formixing properties compared to subunits 5+10, were associated with goodloaf characteristics.     

Association between frost tolerance and the alleles of high molecular weight glutenin subunits present in Polish winter wheats

Subunits of high molecular weight glutenins strongly influence wheat bread making quality and can be associated with important agronomic traits. Polish winter wheats show a significant quantitative dominance of the null allele over the coding alleles of the Glu-A1 locus. To identify the causes of such skewed distribution, 116 F₅ lines obtained from six cross combinations were analyzed for their HMW glutenin subunits and 11 agronomic characteristics, such as plant height and uniformity, leaf blotch and leaf rust resistance, grain yield per plot, number of grains per ear, grain yield per ear, 1000 kernel weight, frost tolerance, total protein content and the SDS-sedimentation value. The SDS-sedimentation value, resistance to leaf blotch and frost tolerance showed statistically significant associations with the status of the Glu-A1 locus. It appears that chromosome 1A with the null allele at Glu-A1 carries a closely linked locus responsible for frost tolerance. With early strong selection for winter hardiness, the null allele of Glu-A1 becomes fixed in advanced breeding materials despite its strong negative impact on the end use quality.     

Kernel hardness and baking quality of wheat — A genetic analysis using chromosome substitution lines

Summary An attempt was made to identify the chromosomal location of genetic control of a few components of wheat quality, using chromosome substitution lines of Cappelle Desprez, Cheyenne, Hope, and Timstein into the recipient variety Chinese Spring.Major factors for kernel hardness and increased baking absorption were found on chromosomes 5D of Cheyenne and Hope, and on 3B, 5D and 7D of Timstein. In Timstein, the presence of one of these chromosomes sufficed to make the wheat kernels hard.Factors for favourable dough properties were identified on a few other chromosomes, different in various varieties. These were 1A of Cappelle Desprez and Cheyenne, 3B of Hope, and 2D of Timstein. All but one of these chromosomes showed an increase in loaf volume to a level in-between those of the recipient variety Chinese Spring and the donor varieties. No relationship was found between kernel hardness and dough-making and baking properties.It was assumed that wheat quality is due to a combination of kernel hardness and favourable dough-making properties. As the genes for these factors are located on different chromosomes, it should not be too difficult to introduce both factors in existing varieties with poor baking properties. In a wheat breeding programme, the quality of new lines can be assessed in a rather simple way by determining kernel hardness and dough stability.     

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.     

Expression of seed storage proteins responsible for maintaining kernel traits and wheat flour quality in common wheat under heat stress conditions

Heat stress during grain filling has been documented to decrease wheat grain yield and quality in arid regions worldwide. We studied the effect of heat stress on wheat flour quality in heat tolerant cultivars to define the effects of heat stress on flour quality and to identify germplasm combining traits for heat tolerance and good flour quality. We studied the kernel phenotypic traits, the expression of seed storage proteins (SSPs), and the resulting flour quality under heat and normal conditions. Under heat stress, all cultivars yielded narrow-shaped seeds, and increased protein contents as compared to the control plants grown under normal conditions. The specific sedimentation values used to estimate the gluten quality varied between cultivars. We identified cultivars that could maintain good flour quality under heat stress conditions: ‘Imam’, which possessed the Glu-D1d allele responsible for the suitable bread-making; ‘Bohaine’, which displayed high expression level of SSPs; and ‘Condor’, which possessed slight variations in the ratio of each SSP under heat stress conditions. Combining the desirable traits from these cultivars could yield a wheat cultivar with heat tolerance and good flour quality.     

Effects of homoeologous group 1 and 6 chromosomes of the Cappelle-Desprez (Bezostaya 1) substitution lines on aspects of bread-making quality of wheat

Summary The group 1 and 6 inter-varietal chromosome substitution lines of Cappelle-Desprez (Bezostaya 1) were intercrossed along with the donor and recipient varieties, Cappelle-Desprez and Bezostaya 1, to give 36 genetically different families. The analysis of the means of these families showed that variation in SDS-sedimentation volume fitted a predominantly additive model. There were no significant within or between chromosome interactions among the group 1 and 6 chromosomes. Nor was there any evidence for interactions between these chromosomes and those of the background. Significant dominance/within chromosome interactions amongst the background chromosomes were however detected. Some of the positive effects on SDS-sedimentation were associated with increased grain hardness. Chromosome effects on % grain protein were not correlated with SDS-sedimentation.     

Dough properties and bread-making quality-related characteristics of Yumechikara near-isogenic wheat lines carrying different Glu-B3 alleles

We investigated the relationships of three allelic variations in Glu-B3 (ab, g, and h) with dough properties and bread-making quality-related characteristics using near-isogenic lines (NILs) of ‘Yumechikara’ that commonly carry Glu-A1a, Glu-B1b, Glu-D1d, Glu-A3f, Glu-B3ab and Glu-D3a. Measurement of peak time (PT) in a 2-g mixograph indicated that Glu-B3g was the most effective for a strong dough property, followed by Glu-B3ab, with Glu-B3h being the least effective. The results of measurement of mixing time during bread-making were similar to those for PTs, i.e., the lines carrying Glu-B3g showed the longest mixing time, followed by those of Glu-B3ab, and those of Glu-B3h showed the shortest mixing time. Since two parameters of bread-making quality, loaf volume (LV) and specific loaf volume (SLV), were affected by flour protein contents in all groups of the Glu-B3 genotype, we compared the effects of the three Glu-B3 alleles on those parameters using analysis of covariance (ANCOVA) to remove the effect of protein content. The results indicated that the Glu-B3h group showed the largest SLV, followed by the Glu-B3ab group, and the Glu-B3g group showed the smallest SLV. These results suggest that the introduction of Glu-B3h into ‘Yumechikara’ makes it possible to breed varieties with good bread-making quality-related characteristics.