Genetic dissection reveals effects of interaction between high-molecular-weight glutenin subunits and waxy alleles on dough-mixing properties in common wheat

The glutenin and waxy loci of wheat are important determinants of dough quality. This study was conducted to evaluate the effects of high-molecular-weight glutenin (HMW-GS) and waxy alleles on dough-mixing properties. Molecular mapping was used to investigate these effects on Mixograph properties in a population of 290 (Nuomai1 × Gaocheng8901) recombinant inbred lines (RILs) from three environments in the harvest years 2008, 2009 and 2011. The results indicated the following: (i) the Glu-A1 and Glu-D1 loci have greater impacts on Mixograph properties compared to the Wx-1 loci and the effects of Glu-D1d and Glu-D1h on dough mixing are better than those of Glu-D1f and Glu-D1new1 in this population; (ii) the interactions between the Glu-1 and Wx-1 loci affected some traits, especially the midline peak value (MPV), and the lack of Wx-B1 or Wx-D1 led to increased MPV for all types of Glu-1 loci; and (iii) 30 quantitative-trait loci (QTL) over nine wheat chromosomes were identified with ICIM analysis based on the genetic map of 498 loci. Eight major QTL and 16 QTL in the Glu-1 loci from the three environments were found. The major QTL clusters were associated with the Glu-1 loci, and also were found in two regions on chromosome 3B and one region on chromosome 6A, which is one of the novel chromosome regions influencing dough-mixing strength. The two QTL for MPV are located around Wx-B1 on chromosome 4A. QMPT-1D.1, QMPI-1D.1 and Q8MW-1D.1 were stable in different environments and could potentially be used in molecular marker-assisted breeding.     

The genetic control of milling yield, dough rheology and baking quality of wheat

Improving the end-use quality of wheat is a key target for many breeding programmes. With the exception of the relationship between glutenin alleles and some dough rheological characters, knowledge concerning the genetic control of wheat quality traits is somewhat limited. A doubled haploid population produced from a cross between two Australian cultivars ‘Trident’ and ‘Molineux’ has been used to construct a linkage map based largely on microsatellite molecular makers. ‘Molineux’ is superior to ‘Trident’ for a number of milling, dough rheology and baking quality characteristics, although by international standards ‘Trident’ would still be regarded as possessing moderately good end-use quality. This population was therefore deemed useful for investigation of wheat end-use quality. A number of significant QTL identified for dough rheological traits mapped to HMW and LMW glutenin loci on chromosomes 1A and 1B. However, QTL associated with dough strength and loaf volume were also identified on chromosome 2A and a significant QTL associated with loaf volume and crumb quality was identified on chromosome 3A. A QTL for flour protein content and milling yield was identified on chromosome 6A and a QTL associated with flour colour reported previously on chromosome 7B was confirmed in this population. The detection of loci affecting dough strength, loaf volume and flour protein content may provide fresh opportunities for the application of marker-assisted selection to improve bread-making quality.     

Molecular detection of QTLs for agronomic and quality traits in a doubled haploid population derived from two Canadian wheats (Triticum aestivum L.)

Development of high-yielding wheat varieties with good end-use quality has always been a major concern for wheat breeders. To genetically dissect quantitative trait loci (QTLs) for yield-related traits such as grain yield, plant height, maturity, lodging, test weight and thousand-grain weight, and for quality traits such as grain and flour protein content, gluten strength as evaluated by mixograph and SDS sedimentation volume, an F₁-derived doubled haploid (DH) population of 185 individuals was developed from a cross between a Canadian wheat variety “AC Karma” and a breeding line 87E03-S2B1. A genetic map was constructed based on 167 marker loci, consisting of 160 microsatellite loci, three HMW glutenin subunit loci: Glu-A1, Glu-B1 and Glu-D1, and four STS-PCR markers. Data for investigated traits were collected from three to four environments in Manitoba, Canada. QTL analyses were performed using composite interval mapping. A total of 50 QTLs were detected, 24 for agronomic traits and 26 for quality-related traits. Many QTLs for correlated traits were mapped in the same genomic regions forming QTL clusters. The largest QTL clusters, consisting of up to nine QTLs, were found on chromosomes 1D and 4D. HMW glutenin subunits at Glu-1 loci had the largest effect on breadmaking quality; however, other genomic regions also contributed genetically to breadmaking quality. QTLs detected in the present study are compared with other QTL analyses in wheat.     

Novel and favorable QTL allele clusters for end-use quality revealed by introgression lines derived from synthetic wheat

Wheat quality is an important target trait. Previous studies mainly focus on storage protein, but their contribution to quality is partial, and most loci for quality are still undetected. Wild species of wheat are valuable resources for wheat improvement and introgression lines (ILs) are the ideal materials for detecting quantitative trait loci (QTL). In this study, a set of 82 BC5 F2-6 ILs, carrying a range of introgressed chromosome segments from a synthetic hexaploid wheat Am3 (Triticum carthlicum × Aegilops tauschii), was developed and genotyped with 170 microsatellite markers. QTL analysis was performed for 14 parameters, sodium dodecyl sulfate sedimentation volume, grain protein content (GPC), grain hardness and 11 mixograph parameters, associated with end-use quality of wheat, using the materials harvested in three environments. This led to the detection of 116 QTL, with c. 95% of the positive alleles contributed by Am3. Six important and novel genomic regions for bread-making quality were found on chromosomes 2D, 3A, 4A, 4B, 5A and 6A. These loci for bread-making quality showed pleiotropy and had large positive effects on several quality parameters with no or very weak negative effect on grain yield, thus demonstrating the value of synthetic wheat as a source of useful genetic variation for the improvement of bread wheat quality.     

水稻外观品质的数量性状基因位点分析

利用由98个家系组成的Nipponbare(粳)／Kasalath(秒)∥Nipponbare回交重组自交系(backcross inbred lines,BILs)群体(BC1F9)及其分子连锁图谱,采用复合区间作图的方法,在2个不同年份对粒长、粒宽、粒形、垩白率、垩白大小、垩白度和透明度等7个稻米外观品质性状的数量性状基因位点(Quantiative trait loci,QTL)进行了定位分析。共定位到33个四QTLs,单个性状QTL数目在4-7个之间,以垩白率最多,为7个;粒长和垩白大小次之,为5个;其他性状均为4个,表明该组合外观品质是由多基因控制的数量性状。单个QTL对性状变异解释率粒长为6．2％-15．2％,粒宽为8．3％-32．5％,长宽比为6．8％-19．8％,垩白率为6．4％-28．5％,垩白大小为6．1％-16．9％,垩白度为9．3％-17．2％,透明度为5．6％-25．2％．QTL在染色体上成集中分布的特点,第3染色体C1488-C563、第5染色体R830-R3166和R1436-R2289、第6染色体R2147-R2171均有3个以上的QTLs分布。比较2年的检测结果表明,外观品质性状的QTL定位都受环境影响,但不同性状受影响的程度差异很大。粒长和粒形的QTL定位受环境影响很小,垩白率、垩白大小和垩白度的QTL定位受环境影响很大。     

Dissecting the genetic basis for the effect of rice chalkiness, amylose content, protein content, and rapid viscosity analyzer profile characteristics on the eating quality of cooked rice using the chromosome segment substitution line population across eight environments

Quantitative trait locus (QTL) mapping and stability analysis were carried out for 16 rice (Oryza sativa L.) quality traits across eight environments, by using a set of chromosome segment substitution lines with 'Asominori' as genetic background. The 16 quality traits include percentage of grain with chalkiness (PGWC), area of chalky endosperm (ACE), amylose content (AC), protein content (PC), peak viscosity, hot paste viscosity, cool paste viscosity, breakdown viscosity (BDV), setback viscosity (SBV), consistency viscosity, cooked-rice luster (LT), scent, tenderness (TD), viscosity, elasticity, and the integrated values of organleptic evaluation (IVOE). A total of 132 additive effect QTLs are detected for the 16 quality straits in the eight environments. Among these QTLs, 56 loci were detected repeatedly in at least three environments. Interestingly, several QTL clusters were observed for multiple quality traits. Especially, one QTL cluster near the G1149 marker on chromosome 8 includes nine QTLs: qPGWC-8, qACE-8, qAC-8, qPC-8a, qBDV-8a, qSBV-8b, qLT-8a, qTD-8a, and qIVOE-8a, which control PGWC, ACE, AC, PC, BDV, SBV, LT, TD, and IVOE, respectively. Moreover, this QTL cluster shows high stability and repeatability in all eight environments. In addition, one QTL cluster was located near the C2340 marker on chromosome 1 and another was detected near the XNpb67 marker on chromosome 2; each cluster contained five loci. Near the C563 marker on chromosome 3, one QTL cluster with four loci was found. Also, there were nine QTL clusters that each had two or three loci; however, their repeatability in different environments was relatively lower, and the genetic contribution rate was relatively smaller. Considering the correlations among all of the 16 quality traits with QTL cluster distributions, we can conclude that the stable and major QTL cluster on chromosome 8 is the main genetic basis for the effect of rice chalkiness, AC, PC, and rapid viscosity analyzer profile characteristics on the eating quality of cooked rice. Consequently, this QTL cluster is a novel gene resource for controlling rice high-quality traits and should be of great significance for research on formation mechanism and molecule improvement of rice quality.     

Genetic analysis of bread-making quality scores in bread wheat using a recombinant inbred line population

Bread-making quality has been evaluated in a progeny of 194 recombinant inbred lines (RILs) from the cross between the two French cultivars Récital and Renan, cultivated in three environments. These cultivars have been previously identified as having contrasting grain protein content and dough rheology properties, although they achieve similar scores for the official bread-making test used for cultivar registration in France. However the progeny displayed a wide range of variations, suggesting that favourable alleles at several loci are present in the two parental lines. Correlation analyses revealed that bread-making scores are poorly correlated among environments, as they are poorly predicted by multiple regression on dough rheology parameters and flour-protein content. However, loaf volume was the most heritable and predictable trait. A total of seven QTLs were found for bread scores, each explaining 5.9–14.6% of trait variation and six for the loaf volume (10.7–17.2%). Most bread-making QTLs, and particularly those detected in all environments, co-located with QTLs for dough rheology, protein content or flour viscosity due to soluble pentosans (Fincher and Stone 1986; Anderson et al. in J Cereal Sci 19:77–82, 1994). Some QTL regions such as those on chromosome 3A and chromosome 7A, which display stable QTLs for bread-making scores and loaf volume, were not previously known to host obvious genes for grain quality.     

谷蛋白聚合体大小分布与面粉揉面特性的初步研究

用单向一步SDS-PAGE方法分析表明小麦品种Suneca和Cook在麦谷蛋白5个亚基位点（Glu-B1,Glu-D1,Glu-A3,Glu-B3和Glu-D3)均含不同等位基因。选用Suneca×Cook的F4代群体中麦谷蛋白亚基位点均为纯合基因的60个系,研究麦谷蛋白基因型不同的株系间谷蛋白聚合体粒度大小分布（用SE-HPLC测定）和面粉揉面特性的变异。结果表明,不同的谷蛋白基因型,其谷蛋白聚合体粒度大小相对分布（用不溶谷蛋白聚合体占总谷蛋白聚合体含量的百分数表示,即UPP%）和面团形成时间（即揉面仪曲线图峰值的和面时间,简写PTM）均有显差异;面粉的揉面曲线形状与其UPP%值密切相关;UPP%与PTM呈极显正相关,与揉面仪曲线图峰高（PHM）呈显负相关;与面粉蛋白质含量（FP%）相比,UPP%对PTM和PHM的影响更大些,可作为育种早代品质性状选择一个指标。     

Mapping of quantitative trait loci (QTL) associated with activity of disulfide reductase and lipoxygenase in grains of durum wheat Triticum aestivum L. seeds

Activity of two enzymes of thiol-disulfide cell metabolism, lipoxygenase (LOX, EC 1.13.11.12) and disulfide-reductase (TPDO, EC 1.8.4.2) was studied in recombinant inbred lines of common wheat ITMI. Their activity in the caryopsis may be connected with the gluten quality, one of the most important traits significant for selection. The activity of lipoxygenase under favorable and droughty environmental conditions was shown to be associated with the quantitative trait locus (QTL) located on chromosome 4BS near the structural gene of a subunit of this enzyme. However, no QTL common to this enzyme and any characteristic of gluten quality have been found. Four loci responsible for the activity of disulfide reductase were identified on chromosomes 4A, 5D, 6A, and7D. Previously, indicators of grain and flour properties, such as elasticity, flour vigor, and grain hardiness were mapped at the same loci. This indicates that the given enzyme participates in the formation of the protein complex upon maturation of wheatgrain. The detected QTL can be involved in further genetic studies designed to establish the regularities of gluten formation.     

Mapping of quantitative trait loci (QTL) associated with activity of disulfide reductase and lipoxygenase in grain of bread wheat <Emphasis Type="Italic">Triticum aestivum</Emphasis> L.

Activity of two enzymes of thiol-disulfide cell metabolism, lipoxygenase (LOX, EC 1.13.11.12) and disulfide-reductase (TPDO, EC 1.8.4.2) was studied in recombinant inbred lines of bread wheat ITMI. Their activity in the caryopsis may be connected with the gluten quality, one of the most important traits significant for breeding. The activity of lipoxygenase under favorable and droughty environmental conditions was shown to be associated with the quantitative trait locus (QTL) located on chromosome 4BS near the structural gene of a subunit of this enzyme. However, no QTL common to this enzyme and any characteristic of gluten quality have been found. Four loci responsible for the activity of disulfide reductase were identified on chromosomes 4A, 5D, 6A, and 7D. Previously, indicators of grain and flour properties, such as elasticity, flour strenght, and grain hardiness were mapped at the same loci. This indicates that the given enzyme participates in the formation of the protein complex upon maturation of wheat grain. The detected QTL can be involved in further genetic studies designed to establish the regularities of gluten formation.     

Genetic dissection of interactions between wheat flour starch and its components in two populations using two QTL mapping methods

Starch content and its components are important for determining wheat end-use quality and yield. However, little information is available about their interactions at the QTL/gene level in more than one population using different QTL mapping methods. Therefore, to dissect these interactions, two mapping populations from two locations over 2 years were used. The QTLs for the populations were analyzed by unconditional and conditional QTL mapping by two different analysis methods. In the two populations, there were a total of 24 unconditional additive QTLs detected for flour amylose (FAMS), flour amylopectin (FAMP), flour total starch (FTSC), and the ratio of FAMS to FAMP using ICIMapping4.1 methods, but 26 unconditional QTLs were found using QTLNetwork2.0 methods. Of these QTLs, 10 stable major additive QTLs were identified in more than one environment, mainly distributed on chromosomes 3B, 4A, 5A, and 7D. The maximum percentage of phenotypic variance explained (PVE) reached 54.31%. Two new unconditional major additive QTLs on chromosome 3B (Qftsc3B and Qfamp3B) were found. A total of 23 and 19 conditional additive QTLs were identified in the two populations using two different methods, respectively. Of which, eight and six stable major conditional QTLs were detected on chromosomes 3B, 4A, and 7D, respectively. New repressed QTLs were identified, such as Qftsc/fams5B-1 and Qftsc/fams5B-2. There were 20 epistatic unconditional and 15 conditional QTLs detected. In all, important QTLs on chromosomes 3B, 4A, and 7A were found in both populations. However, the number of important QTLs in the special recombinant inbred line (RIL) population was higher than that in the double haploid (DH) population, especially on chromosomes 7D and 5B. Moreover, the QTLs on chromosomes 4A, 7A, and 7D were close to the Wx-1 loci in the RIL population. These indicated better results can be obtained by a special population to target traits than by a common population. The important QTLs on key chromosomes can always be detected no matter what kinds of populations are used, such as the QTLs on chromosome 4A. In addition, QTL clusters were found on chromosomes 4A, 3B, 7A, 7D, and 5A in the two populations, indicating these chromosome regions were very important for starch biosynthesis.     

Homoeologous recombination within bread wheat to develop novel combinations of HMW-GS genes: transfer of the <Emphasis Type="Italic">Glu-A1</Emphasis> locus to chromosome 1D

In an attempt to improve the bread-making quality within hexaploid wheat by elaborating novel high-molecular weight glutenin subunits (HMW-GS) combinations useful in wheat-breeding programmes, a 1A chromosome fragment carrying the Glu-A1 locus encoding the subunit Ax2*, was translocated to the long arm of chromosome 1D. The partially isohomoeoallelic line, designated RR239, had a meiotic behaviour as regular as cv. Courtot. It was characterised using genomic in situ hybridization and microsatellite markers as well as biochemical and proteomic approaches. The translocated 1D chromosome had an interstitial 1AL segment representing in average 30% of the recombinant arm length that was confirmed by molecular analysis. The genetic length of the removed segment in chromosome 1DL was estimated to be at least 51 cM, and that of the interstitial 1AL translocation to be at least 33 cM. Proteome analysis performed on total endosperm proteins revealed variation in amounts, 8 spots and 1 spot being up- and downregulated, respectively. Quantitative variations in HMW-GS were observed for the Glu-A1 (Ax2*) and Glu-B1 (Bx7 + By8) loci in response to duplication of the Glu-A1 locus.     

QTL analysis of bread-making quality in wheat using a doubled haploid population

A set of 187 doubled haploid lines derived from the cross between cvs. Courtot and Chinese Spring was explored for QTLs for three bread-making quality tests: hardness, protein content and strength of the dough (W of alveograph). The scores of the parental lines were quite different except for protein content, and the population showed a wide range of variation. About 350 molecular and biochemical markers were used to establish the genetic map, and technological criteria were evaluated in 1 to 3 years. QTL detection was performed by the ”marker regression” method. The most significant unlinked markers were used in the model as covariates, and the results were tested by bootstrap resampling. For hardness, we confirmed a previously tagged major QTL on chromosome 5DS, and two additional minor QTLs were found on chromosome 1A and 6D, respectively. For protein content two main QTLs were identified on chromosomes 1B and 6A, respectively. For W, three consistent QTLs were detected: two at the same location as those for hardness, on chromosomes 1A and 5D; the third one on chromosome 3B. Therefore, it appeared that except for the Glu-1A locus, storage protein loci were not clearly involved in the genetic control of the criteria studied in the present work. Despite the reasonable size of the population no QTL with interactive effects could be substantially established as measured. All computations were carried out using home-made programmes in Splus language, and these are available upon request. Received: 16 May 1999 / Accepted: 15 October 1999     

Genomic regions influencing gene expression of the HMW glutenins in wheat

Bread wheat (Triticum aestivum L.) produces glutenin storage proteins in the endosperm. The HMW glutenins confer distinct viscoelastic properties to bread dough. The genetics of HMW glutenin proteins have been extensively studied, and information has accumulated about individual subunits, chromosomal locations and DNA sequences, but little is known about the regulators of the HMW glutenins. This investigation addressed the question of glutenin regulators. Expression of the glutenins was analyzed using QRT-PCR in ditelosomic (dt) Chinese Spring (CS) lines. Primers were designed for each of 4 CS glutenin genes and a control, non-storage protein endosperm-specific gene Agp-L (ADP-glucose pyrophosphorylase). Each line represents CS wheat, lacking one chromosome arm. The effect of a missing arm could feasibly cause an increase, decrease or no change in expression. For each HMW glutenin, results indicated there were, on average, 8 chromosome arms with an up-regulatory effect and only one instance of a down-regulatory effect. There were significant correlations between orthologous and paralogous HMW glutenins for effects of chromosome groups B and D. Some or all the glutenin alleles shared regulatory loci on chromosome arms 2BS, 7BS, 4DS, 5DS and 6DS, and Agp-L shared regulatory loci with glutenins on arms 7AS, 7BS, 2DS, 3DS, 4DS and 5DS. These results suggest a few chromosome arms contain putative regulatory genes affecting the expression of conserved cis elements of 4 HMW glutenin and Agp-L genes in CS. Regulation by common genes implies the regulators have diverged little from the common wheat ancestor, and furthermore, some regulation may be shared by endosperm-specific-genes. Significant common regulators have practical implications.     

Immunochemical identification of LMW subunits of glutenin associated with bread-making quality of wheat flours

A murine monoclonal antibody (IFRN 0067), one of a library developed against prolamin fractions fromTriticum aestivum, has been characterised using a combination of immunoassay and immunoblotting techniques. The antibody was specific for two glutenin polypeptides which appeared by 2-dimensional electrophoresis to belong to the B group of LMW subunits. From results of antibody-binding studies with material extracted from genetic stocks, it was deduced that the target polypeptides were encoded on the short arm of chromosome 1D. The antibody was used in an immunoassay of bread wheats with a range of anticipated baking scores and for flours of known baking performance. Significant correlations were found between immunoassay and test-bake results. Indeed, correlation of IFRN 0067 binding with loaf volume was equal or better than that provided by alveograph parameters. The results provide evidence that LMW subunits contribute to the bread-making properties of wheat glutenin, as identified by the use of immunological techniques. The use of particular monoclonal antibodies, such as IFRN 0067, in the further development of simple, rapid diagnostic tests for flour quality predictions is discussed.     

Mapping of the quantitative trait loci (QTL) associated with grain quality characteristics of the common wheat grown under different environmental conditions

The quantitative trait loci (QTL) associated with individual characteristics of grain and flour quality in wheat lines grown under contrasting environmental conditions were mapped. Overall, 22 QTL that manifested under contrasting environmental conditions with various significances were detected on 10 chromosomes. Grain hardness and vitreousness were associated with three loci on chromosomes 5D, 6A, and 3A, while the gluten content, with two loci on chromosomes 5B and 7A. Dough extensibility was associated with only one QTL localized in the region of Glu-A1 locus. One of the loci determining flour and dough strengths is located in the region of Gli-B1 and Glu-B3 loci and the rest, in various regions of chromosomes 1B, 5D, and 4B, where no particular genes associated with grain quality have been yet found. The detected QTL can be used in further experiments on genetic control of gluten formation and quality in wheat.     

New insights into the organization, recombination, expression and functional mechanism of low molecular weight glutenin subunit genes in bread wheat

The bread-making quality of wheat is strongly influenced by multiple low molecular weight glutenin subunit (LMW-GS) proteins expressed in the seeds. However, the organization, recombination and expression of LMW-GS genes and their functional mechanism in bread-making are not well understood. Here we report a systematic molecular analysis of LMW-GS genes located at the orthologous Glu-3 loci (Glu-A3, B3 and D3) of bread wheat using complementary approaches (genome wide characterization of gene members, expression profiling, proteomic analysis). Fourteen unique LMW-GS genes were identified for Xiaoyan 54 (with superior bread-making quality). Molecular mapping and recombination analyses revealed that the three Glu-3 loci of Xiaoyan 54 harbored dissimilar numbers of LMW-GS genes and covered different genetic distances. The number of expressed LMW-GS in the seeds was higher in Xiaoyan 54 than in Jing 411 (with relatively poor bread-making quality). This correlated with the finding of higher numbers of active LMW-GS genes at the A3 and D3 loci in Xiaoyan 54. Association analysis using recombinant inbred lines suggested that positive interactions, conferred by genetic combinations of the Glu-3 locus alleles with more numerous active LMW-GS genes, were generally important for the recombinant progenies to attain high Zeleny sedimentation value (ZSV), an important indicator of bread-making quality. A higher number of active LMW-GS genes tended to lead to a more elevated ZSV, although this tendency was influenced by genetic background. This work provides substantial new insights into the genomic organization and expression of LMW-GS genes, and molecular genetic evidence suggesting that these genes contribute quantitatively to bread-making quality in hexaploid wheat. Our analysis also indicates that selection for high numbers of active LMW-GS genes can be used for improvement of bread-making quality in wheat breeding.     

Genetic characterisation of dough rheological properties in a wheat doubled haploid population: additive genetic effects and epistatic interactions

Doubled haploid lines (n=160) from a cross between wheat cultivars Cranbrook (high dough extensibility) and Halberd (low dough extensibility) were grown at three Australian locations. The parents differ at all high- and low-molecular-weight glutenin loci. Dough rheological parameters were measured using small-scale testing procedures, and quantitative trait locus (QTL) mapping procedures were carried out using an existing well-saturated genetic linkage map for this cross. Genetic parameters were estimated using three software packages: QTLCartographer, Epistat and Genstat. Results indicated that environmental factors are a major determinant of dough extensibility across the three trial sites, whereas genotypic factors are the major determinants of dough strength. Composite interval mapping analysis across the 21 linkage groups revealed that as expected, the main additive QTLs for dough rheological properties are located at the high- and low-molecular-weight glutenin loci. A new QTL on chromosome 5A for M-extensibility (a mixograph-estimated measure of extensibility) was detected. Analysis of epistatic interactions revealed that there were significant conditional epistatic interactions related with the additive effects of glutenin loci on dough rheological properties. Therefore, the additive genetic effects of glutenins on dough rheological properties are conditional upon the genetic background of the wheat line. The molecular basis of the interactions with the glutenin loci may be via proteins that modify or alter the gluten protein matrix or variations in the expression level of the glutenin genes. Reverse-phase high performance liquid chromatography analysis of the molar number of individual glutenin subunits across the population showed that certain conditional epistases resulted in increased expression of the affected glutenin. The epistatic interactions detected in this study provide a possible explanation of the variable genetic effects of some glutenins on quality attributes in different genetic backgrounds and provide essential information for the accurate prediction of glutenin related variance in marker-assisted wheat breeding.     

Proteomic analysis of aneuploid lines in the homeologous group 1 of the hexaploid wheat cultivar Courtot

Three monosomic lines (MSLs) and three nullisomic lines (NSLs) of the homeologous group 1 and one euploid line of the bread wheat Triticum aestivum cultivar Courtot were used in a proteomic approach to investigate the effects of zero, one or two doses of chromosomes 1A, 1B and 1D on the amount of endosperm proteins. Polypeptides whose amounts changed significantly between each aneuploid line and the euploid line were identified using image analyses of two-dimensional gel electrophoresis patterns resulting from specific endosperm protein extractions. Matrix-assisted laser desorption/ionization-time of flight mass spectrometry and electrospray ionization tandem mass spectrometry were also used for protein identification. Removing one chromosome or a chromosome pair allowed varying responses to be observed for the remaining endosperm protein genes. Compensation phenomena for the high molecular weight glutenin subunits (HMW-GS) were detected only in the MSLs. Subunits Bx7, By8 and Dy12 were the only HMW-GS overexpressed (from 152-737%) when chromosomes 1A or 1B or 1D were at hemizygous state. Thirteen new protein spots were detected only in the NSL1D, and seven were identified as HMW-GS analogs. These seven new spots may result from the expression of inactive genes. The HMW-GS were of significantly higher volume in MSLs, whereas the low molecular weight glutenin subunits and the gamma-gliadins were of lower volume in aneuploid lines. Most of the down-regulated proteins in the MSLs were storage proteins encoded at loci located on another chromosome pair. Complex regulations between chromosomes and loci of the homeologous groups 1 and 6 in bread wheat are discussed.     

Mapping of the quantitative trait loci (QTL) associated with grain quality characteristics of the bread wheat grown under different environmental conditions

The quantitative trait loci (QTL) associated with individual characteristics of grain and flour quality in wheat lines grown under contrasting environmental conditions were mapped. Overall, 22 QTL that manifested under contrasting environmental conditions with various significances were detected on 10 chromosomes. Grain hardness and vitreousness were associated with three loci on chromosomes 5D, 6A, and 3A, while the gluten content, with two loci on chromosomes 5B and 7A. Dough extensibility was associated with only one QTL localized in the region of Glu-A1 locus. One of the loci determining flour and dough strengths is located in the region of Gli-B1 and Glu-B3 loci and the rest, in various regions of chromosomes 1B, 5D, and 4B, where no particular genes associated with grain quality have been yet found. The detected QTL can be used in further experiments on genetic control of gluten formation and quality in wheat.