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.     

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.     

Genetic diversity of bread wheat genotypes in Iran for some nutritional value and baking quality traits

Genetic variation among 78 irrigated bread wheat genotypes was studied for their nutritional value and baking quality traits as well as some agronomic traits. The experiment was conducted in a randomized complete block design with three replicates under normal and terminal drought stress conditions in Kermanshah, Iran during 2012–2013 cropping season. The results of combined ANOVA indicated highly significant genotypic differences for all traits. All studied traits except grain yield, hectoliter weight and grain fiber content were significantly affected by genotype × environment interaction. Drought stress reduced grain yield, thousand kernel weight, gluten index, grain starch content and hectoliter weight and slightly promoted grain protein and fiber contents, falling number, total gluten and ratio of wet gluten to grain protein content. Grain yield by 31.66% and falling number by 9.20% attained the highest decrease and increase due to drought stress. There were negative and significant correlations among grain yield with grain protein and fiber contents under both conditions. Results of cluster analysis showed that newer genotypes had more grain yield and gluten index than older ones, but instead, they had the lower grain protein and fiber contents. It is thought that wheat breeders have bred cultivars with high grain yield, low protein content, and improved bread-making attributes during last seven decades. While older genotypes indicated significantly higher protein contents, and some of them had higher gluten index. We concluded from this study that it is imperative for breeders to pay more attention to improve qualitative traits coordinated to grain yield.     

Relationship between the dough quality and content of specific glutenin proteins in wheat mill streams, and its application to making flour suitable for instant Chinese noodles

The content of specific proteins such as high-molecular-weight glutenin subunits HMW-GS 5+10 and low-molecular-weight glutenin subunits LMW-GS KS2 in wheat mill streams of extra-strong Kachikei 33 wheat was quantified by SDS-PAGE and 2D-PAGE. The mill streams showed varied quantities of HMW-GS 5+10 (0.077 to 2.007 mg/g of mill stream), LMW-GS KS2 (0.018 to 0.586 mg/g of mill stream) and total protein (9.42% to 18.98%). The contents of these specific proteins in the mill streams were significantly correlated with the SDS sedimentation volume and the mixing properties, which are respective indices of specific loaf volume and dough strength. The contents of these specific glutenin proteins in the mill streams were therefore found to be significantly important for improving the dough quality suitable for bread and Chinese noodles. Accordingly, we present here the application of this information to the development of an effective method for producing mill streams with high quality and yield that are suitable for instant Chinese noodles.     

Genetic analysis of dry matter and nitrogen accumulation and protein composition in wheat kernels

The maximum rate and duration for grain dry matter (DM) and nitrogen (N) accumulation were evaluated in 194 recombinant inbred lines (RILs) from a cross between the two French wheat cultivars Récital and Renan. These cultivars were previously identified as having contrasting kinetics of grain DM and N accumulation. Grain protein composition was analysed by capillary electrophoresis (CE), which enabled quantification of the different storage protein fractions (-gliadins, -gliadins, LMW glutenins, HMW glutenins, and each of their subunits). Correlation analyses revealed that DM and N accumulation rates were closely correlated and repeatable over several years, which was not the case for DM and N accumulation durations, and that protein composition was primarily influenced by the N accumulation rate. This was particularly true for the LMW-glutenins and the -gliadins, the most abundant protein fractions. A genetic map of 254 molecular markers covering nearly 80% of the wheat genome was used for quantitative trait loci (QTL) analysis. A total of seven QTLs were found. Five QTLs were significantly associated with the kinetics of DM and N accumulation, and two of them also influenced protein composition. Two QTLs affected only the protein composition. One major QTL explained more than 70% of the total variation in HMW-GS Glu1B-x content.     

小麦贮藏蛋白与小麦品质性状的关系及研究进展

小麦贮藏蛋白尤其是谷蛋白与醇溶蛋白的组成及所占比例是影响小麦加工品质的主要因素。本文对近年来国内外小麦蛋白亚基和小麦品质性状的研究现状进行了综述,同时介绍了小麦品质性状的遗传规律及其与品质的关系。     

Genetic relationships between composition of pork bellies and performance, carcase and meat quality traits

Belly traits including predicted fat percentage of the belly (FATPC), combined area of the rib bone and muscle (RBMA), intermuscular fat area (IMFA) and subcutaneous fat area (SFA) were recorded on 2403 pigs along with carcase fat depth at the P2 site (P2). Belly traits were derived from image analysis of the anterior side of pork bellies. Further data available for pigs with belly data and their contemporaries included lifetime growth rate, ultrasound backfat and loin muscle depth (35 406 records), along with meat quality traits (3935 records). There were 4586 feed intake records and 18 398 juvenile insulin-like growth factor-I (IGF-I) records available, which included the majority of pigs with belly data. Genetic parameters were estimated based on an animal model using Residual Maximum Likelihood procedures. Heritability estimates for belly traits ranged from 0.23 to 0.34 (±0.05 to 0.06) while the common litter effect varied from 0.04 to 0.07 (±0.03). Genetic correlations between FATPC, individual belly fat measurements and carcase P2 fat depth differed significantly from unity, ranging from 0.71 to 0.85 (±0.05 to 0.08). Genetic correlations between IMFA and subcutaneous fat measurements varied from 0.47 to 0.63 (±0.08 to 0.13). Genetic correlations between belly and performance traits show that selection for reduced juvenile-IGF-I, reduced feed intake and reduced backfat along with increased loin muscle depth will reduce overall fat levels in the belly. Only loin muscle depth had a significant genetic correlation with RBMA (0.32 ± 0.10), thereby assisting selection for improved lean meat content of the belly. Ultimately, genetic improvement of belly muscles requires specific measurements of lean meat content of the belly. For this to be effective, measurements are required that can be routinely recorded on the slaughter line, or preferably on the live animal.     

Genetic control and chromosomal location of Triticum timopheevii-derived resistance to septoria nodorum blotch in durum wheat.

The genetic control of resistance, expressed as restricted lesion development in seedling plants, to septoria nodorum blotch of wheat was studied under controlled environmental conditions, using the parental, F1, F2, F3, BC1F1, and BC1F2 generations of crosses of Triticum timopheevii-derived resistant durum lines S3-6, S9-10, and S12-1 with the susceptible durum cv. Sceptre. The seedling resistance of these three resistant sources, derived from T. timopheevii (PI 290518), was monogenically controlled. The chromosomal location of the resistance gene identified was determined by crossing the complete set of 'Langdon' - 'Chinese Spring' D-genome disomic substitution lines with S12-1. Tests of the F1 and F2 generations of each cross indicated that only chromosome 3A was associated with resistance. Therefore, the resistance gene is considered to be located on chromosome 3A and has been designated temporarily as SnbTM.     

Genetic control of embryo lethality in crosses between common wheat and rye

The phenotypic manifestation and genetic control of embryo lethality observed in crosses between common wheat and rye were studied. It was found that crosses between common wheat and inbred self-fertile rye lines L2 and 535 gave rise to ungerminating grains, in which the development and differentiation of the hybrid embryo are arrested. Study of the degree of embryo development in the hybrid grains obtained by crossing common wheat varieties with inbred rye lines L2 and 535 showed that genotypes of the parents affected the ratio between undifferentiated embryos of various sizes. Analysis of this trait was performed by test crosses according to a novel pedigree program with the use of interlinear hybrids and a set of fourth-generation hybrid recombinant inbred lines. Rye line L2 was shown to bear the Eml (Embryo lethality) gene, which terminates the development of the hybrid embryo in amphihaploids. The suggestion of complementary interaction between wheat and rye genes during formation of a "n ew" character in wheat-rye F1 hybrids is discussed. A method of detecting an allele not complementary to the rye Eml allele in wheat is proposed. The proposed test program allows appropriate study of the system of wheat and rye genes involved in complementary interaction in the genotype of a distant hybrid.     

土壤肥力对小麦籽粒蛋白质组分含量及加工品质的影响

研究了基础土壤肥力对小麦籽粒蛋白质组分含量变化及加工品质的影响。结果表明,高肥力土壤栽培的小麦比低肥力土壤栽培的小麦,其籽粒蛋白质及各组分含量都显著提高,但清蛋白和球蛋白占总蛋白含量的比例为低肥力土壤高于高肥力土壤,而醇溶蛋白和麦谷蛋白为高肥力土壤高低肥力土壤;低肥力土壤栽培的小麦籽粒醇溶蛋白开始形成的时间比高肥力的早,高肥力土壤栽培小麦的籽粒醇溶蛋白和麦谷蛋白含量的提高主要源于灌浆后期合成的快,高肥力土壤垢小麦湿面筋含量,沉降值,吸水率,面团形成时间,稳定时间,断裂时间和评价值均显著或极显著高于或长于低肥力的。     

Protein array staining methods for undefined protein content, manufacturing quality control, and performance validation

Methods to assess the quality and performance of protein microarrays fabricated from undefined protein content are required to elucidate slide-to-slide variability and interpolate resulting signal intensity values after an interaction assay. We therefore developed several simple total- and posttranslational modification-specific, on-chip staining methods to quantitatively assess the quality of gel element protein arrays manufactured with whole-cell lysate in vitro protein fractions derived from two-dimensional liquid-phase fractionation (PF2D) technology. A linear dynamic range of at least 3 logs was observed for protein stains and immobilized protein content, with a lower limit of detection at 8 pg of protein per gel element with Deep Purple protein stain and a field-portable microarray imager. Data demonstrate the successful isolation, separation, transfer, and immobilization of putative transmembrane proteins from Yersinia pestis KIM D27 with the combined PF2D and gel element array method. Internal bovine serum albumin standard curves provided a method to assess on-chip PF2D transfer and quantify total protein immobilized per gel element. The basic PF2D array fabrication and quality assurance/quality control methods described here therefore provide a standard operating procedure and basis for developing whole-proteome arrays for interrogating host-pathogen interactions, independent of sequenced genomes, affinity tags, or a priori knowledge of target cell composition.     

Genetic parameters for lactation traits of milking ewes: protein content and composition,fat, somatic cells and individual laboratory cheese yield

The effects of some environmental variation factors and the genetic parameters for total milk traits (fat content, protein content, casein content, serum protein content, lactation mean of individual laboratory cheese yield (LILCY), lactation mean of somatic cell count (LSCC), and milk yield) were estimated from the records of 1 111 Churra ewes. Genetic parameters were estimated by multivariate REML. Heritability for fat content was low (0.10) as is usually found in the Churra breed. Heritabilities for protein content, casein content, serum protein content, LILCY, milk yield and somatic cell count were 0.31, 0.30, 0.22, 0.09, 0.26 and 0.11, respectively. The highest heritability estimates were for protein and casein contents. Casein content is not advisable as an alternative to protein content as a selection criterion for cheese yield improvement; it does not have any compelling advantages and its measurement is costly. Our results for LSCC indicated that efforts should focus on improving the level of management rather than selecting for somatic cells, in the actual conditions of the Churra breed.     

Lipid-mediated interactions between intrinsic membrane proteins: dependence on protein size and lipid composition.

The present study is an application of an approach recently developed by the authors for describing the structure of the hydrocarbon chains of lipid-bilayer membranes (LBMs) around embedded protein inclusions ( Biophys. J. 79:2867-2879). The approach is based on statistical mechanical integral equation theories developed for the study of dense liquids. First, the configurations extracted from molecular dynamics simulations of pure LBMs are used to extract the lateral density-density response function. Different pure LBMs composed of different lipid molecules were considered: dioleoyl phosphatidylcholine (DOPC), palmitoyl-oleoyl phosphatidylcholine (POPC), dipalmitoyl phosphatidylcholine (DPPC), and dimyristoyl phosphatidylcholine (DMPC). The results for the lateral density-density response function was then used as input in the integral equation theory. Numerical calculations were performed for protein inclusions of three different sizes. For the sake of simplicity, protein inclusions are represented as hard smooth cylinders excluding the lipid hydrocarbon core from a small cylinder of 2.5 A radius, corresponding roughly to one aliphatic chain, a medium cylinder of 5 A radius, corresponding to one alpha-helix, and a larger cylinder of 9 A radius, representing a small protein such as the gramicidin channel. The lipid-mediated interaction between protein inclusions was calculated using a closed-form expression for the configuration-dependent free energy. This interaction was found to be repulsive at intermediate range and attractive at short range for two small cylinders in POPC, DPPC, and DMPC bilayers, whereas it oscillates between attractive and repulsive values in DOPC bilayers. For medium size cylinders, it is again repulsive at intermediate range and attractive at short range, but for every model LBM considered here. In the case of a large cylinder, the lipid-mediated interaction was shown to be repulsive for both short and long ranges for the DOPC, POPC, and DPPC bilayers, whereas it is again repulsive and attractive for DMPC bilayers. The results indicate that the packing of the hydrocarbon chains around protein inclusions in LBMs gives rise to a generic (i.e., nonspecific) lipid-mediated interaction which favors the association of two alpha-helices and depends on the lipid composition of the membrane.     

Genetic control of amylose content in wheat endosperm starch and differential effects of three Wx genes

The endosperm starch of the wheat grain is composed of amylose and amylopectin. Genetic manipulation of the ratio of amylose to amylopectin or the amylose content could bring about improved texture and quality of wheat flour. The chromosomal locations of genes affecting amylose content were investigated using a monosomic series of Chinese Spring (CS) and a set of Cheyenne (CNN) chromosome substitution lines in the CS genetic background. Trials over three seasons revealed that a decrease in amylose content occurred in monosomic 4A and an increase in monosomic 7B. Allelic variation between CS and CNN was suggested for the genes on chromosomes 4A and 7B. To examine the effects of three Waxy (Wx) genes which encode a granule-bound starch synthase (Wx protein), the Wx proteins from CS monosomics of interest were analyzed using SDS-PAGE. The amount of the Wx protein coded by the Wx-B1 gene on chromosome arm 4AL was reduced in monosomic 4A, and thus accounted for its decreased amylose content. The amounts of two other Wx proteins coded by the Wx-A1 and Wx-D1 genes on chromosome arms 7AS and 7DS, respectively, showed low levels of protein in the monosomics but no effect on amylose content. The effect of chromosome 7B on the level of amylose suggested the presence of a regulator gene which suppresses the activities of the Wx genes.     

部分美国小麦种质资源醇溶蛋白遗传多样性分析及其亚基对品质性状的影响

为了解67份美国材料的遗传多样性及其醇溶蛋白亚基对品质性状的影响,利用酸性聚丙烯酰胺凝胶电泳(APAGE)技术进行醇溶蛋白谱带分析,测定了面团流变学特性及理化品质。结果表明,在67份美国材料中共分离出1332条谱带,49种不同迁移率类型的谱带,大部分谱带具有多态性。单个材料谱带总数变异幅度为13~28。谱带数在α、β、γ、ω4个区的分布存在较大差异。没有发现电泳谱带完全相同的材料。GS值变异范围0.54~0.90,平均值为0.731。在GS=0.607水平上,聚类分析将这67份材料分为6类。49条不同迁移率的谱带中有17条谱带与36项品质性状的相关性达到显著或极显著差异。6条谱带(迁移率为49.6、56.2、56.7、62.2、79.4、86.8)与湿面筋含量、蛋白质含量和沉淀值呈正相关,而迁移率为60.5的谱带与之呈负相关。11条谱带(迁移率为26.5、42.0、49.6、52.5、56.2、56.7、62.2、64.1、72.0、79.4、86.8)与面团稳定时间、面团形成时间、延伸面积等面团流变学特征呈正相关,而迁移率为34.4、47.5、49.0、60.5、69.4、85.4的6条谱带则与之呈负相关。说明供试材料间存在着丰富的遗传多样性以及与优质品质相关的谱带,为进一步利用这67份种质资源和优质小麦品种的选育提供了理论依据。     

Opportunities for manipulating the seed protein composition of wheat and barley in order to improve quality

Wheat and barley are the major temperate cereals, being used for food, feed and industrial raw material. However, in all cases the quality may be limited by the amount, composition and properties of the grain storage proteins. We describe how a combination of biochemical and molecular studies has led to an understanding of the molecular basis for breadmaking quality in wheat and feed quality in barley, and also provided genes encoding key proteins that determine quality. The control of expression of these genes has been studied in transgenic tobacco plants and by transient expression in cereal protoplasts, providing the basis for the production of transgenic cereals with improved quality characteristics.     

Localization of genes, determining quantitative traits in wheat: amendment to the "catalog of chromosomal mapping of genes in domestic cultivars of wheat"

An amendment to the catalog of chromosome location of genes in Russian wheat cultivars was constructed with the published data of the recent decade. The results of chromosomal localization were summarized and analyzed by methods of multivariate statistics. Chromosomes critical for 40 quantitative traits under study proved to cluster according to their homeology, i.e., by homeological groups. The hypotheses providing an explanation for this finding are considered. It is suggested that quantitative traits are similarly controlled by genes located on homeological chromosomes in common wheat, making it possible to isolate a limited number of major genes for each particular quantitative trait.     

Simulations of dynamically cross-linked actin networks: Morphology,rheology, and hydrodynamic interactions

Cross-linked actin networks are the primary component of the cell cytoskeleton and have been the subject of numerous experimental and modeling studies. While these studies have demonstrated that the networks are viscoelastic materials, evolving from elastic solids on short timescales to viscous fluids on long ones, questions remain about the duration of each asymptotic regime, the role of the surrounding fluid, and the behavior of the networks on intermediate timescales. Here we perform detailed simulations of passively cross-linked non-Brownian actin networks to quantify the principal timescales involved in the elastoviscous behavior, study the role of nonlocal hydrodynamic interactions, and parameterize continuum models from discrete stochastic simulations. To do this, we extend our recent computational framework for semiflexible filament suspensions, which is based on nonlocal slender body theory, to actin networks with dynamic cross linkers and finite filament lifetime. We introduce a model where the cross linkers are elastic springs with sticky ends stochastically binding to and unbinding from the elastic filaments, which randomly turn over at a characteristic rate. We show that, depending on the parameters, the network evolves to a steady state morphology that is either an isotropic actin mesh or a mesh with embedded actin bundles. For different degrees of bundling, we numerically apply small-amplitude oscillatory shear deformation to extract three timescales from networks of hundreds of filaments and cross linkers. We analyze the dependence of these timescales, which range from the order of hundredths of a second to the actin turnover time of several seconds, on the dynamic nature of the links, solvent viscosity, and filament bending stiffness. We show that the network is mostly elastic on the short time scale, with the elasticity coming mainly from the cross links, and viscous on the long time scale, with the effective viscosity originating primarily from stretching and breaking of the cross links. We show that the influence of nonlocal hydrodynamic interactions depends on the network morphology: for homogeneous meshworks, nonlocal hydrodynamics gives only a small correction to the viscous behavior, but for bundled networks it both hinders the formation of bundles and significantly lowers the resistance to shear once bundles are formed. We use our results to construct three-timescale generalized Maxwell models of the networks.