Wheat End-use Quality Research Articles

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.

Evaluation of maternal parent and puroindoline allele on kernel texture in a reciprocal cross between two hard spring wheat cultivars

Kernel texture is an important characteristic for both the milling and the end-use quality of wheat (Triticum aestivum L.). Gene sequence variation and mutations to the two puroindoline genes (Pina and Pinb), located at the Ha locus on chromosome 5DS, account for the majority of variation in wheat kernel texture. Other factors also influence kernel texture, including effects associated with different maternal parent backgrounds. To investigate the effect of two hard puroindoline alleles in different maternal backgrounds, a population of 228 recombinant inbred lines (RILs) derived from a reciprocal cross between two wheat cultivars ‘ID377s’ (Pina-D1b/Pinb-D1a) and ‘Klasic’ (Pina-D1a/Pinb-D1b) were examined in two succeeding generations (F7 & F8). Kernel texture was determined using the Single Kernel Characterization System (SKCS) and the RIL puroindoline haplotype was identified by the sequence-specific PCR amplification of each gene. Analysis of variance identified a significant (P ≤ 0.001) effect of the maternal parent and puroindoline mutation on kernel texture. RILs containing the Pina-D1b mutation were significantly harder than lines containing the Pinb-D1b mutation. RILs which had Klasic as the maternal parent were significantly harder than those which had ID377s as the maternal parent. When the maternal parent and puroindoline allele were analyzed in combination, RILs derived from Klasic as the maternal parent and the Pina-D1b allele were significantly harder (P ≤ 0.001) than those containing the same allele but ID377s as the maternal parent. The same occurred for RILs containing the Pinb-D1b allele, lines with Klasic as the maternal parent were harder than lines with ID377s as the maternal parent. These results corroborate the harder phenotype of the Pina-D1b allele and indicate a significant maternally-inherited contribution to kernel texture variation.

Effect of Multiple Copies of Puroindoline Genes on Grain Softness

End use quality in wheat (Triticum aestivum L.) is primarily determined by grain hardness or texture. The puroindoline genes Pina and Pinb are the main components of the 15‐kDa friabilin protein, which is associated with kernel softness. Pina and Pinb are expressed in diploid wheat species but are silent in tetraploid wheat. The active puroindolines in hexaploid, or bread wheat, were derived from Aegilops tauschii Coss., the D genome diploid donor. The focus of this study was to incorporate active puroindoline genes into the A and B genomes of bread wheat and analyze their impact upon grain softness. Functional copies of Pina and Pinb in disomic substitution lines of T. monococcum L. chromosome 5Am for 5A of T. aestivum and 5Ss of Aegilops searsii Feldman & Kislev ex K. Hammer for 5B of T. aestivum were used to produce lines that contained four copies (5Am, 5D; 5Ss, 5D) and six copies (5Am, 5Ss, 5D) of the puroindolines. There was a direct correlation in grain softness with the increase in copy number of the puroindolines. Northern blots showed increased expression of both Pina and Pinb Extraction of TX114 soluble proteins indicated that levels of both proteins were also increased. Single kernel characterization system (SKCS) analysis showed a decrease in kernel hardness by approximately 10 points below the value of 71 for ‘Chinese Spring’ (CS) for each additional copy of Pina and Pinb added. These results indicate that increasing the functional copy number of the puroindolines can impact grain softness in bread wheat.

Mass spectrometry and partial least-squares regression: a tool for identification of wheat variety and end-use quality.

Rapid methods for the identification of wheat varieties and their end-use quality have been developed. The methods combine the analysis of wheat protein extracts by mass spectrometry with partial least-squares regression in order to predict the variety or end-use quality of unknown wheat samples. The whole process takes approximately 30 min. Extracts of alcohol-soluble storage proteins (gliadins) from wheat were analysed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Partial least-squares regression was subsequently applied using these mass spectra for making models that could predict the wheat variety or end-use quality. Previously, an artificial neural network was used to identify wheat varieties based on their protein mass spectra profiles. The present study showed that partial least-squares regression is at least as useful as neural networks for this identification. Furthermore, it was demonstrated that partial least-squares regression could be used to predict wheat end-use quality, which has not been possible using neural networks.

Hordoindolines are associated with a major endosperm-texture QTL in barley (Hordeum vulgare).

Endosperm texture has a tremendous impact on the end-use quality of wheat (Triticum aestivum L.). Cultivars of barley (Hordeum vulgare L.), a close relative of wheat, also vary measurably in grain hardness. However, in contrast to wheat, little is known about the genetic control of barley grain hardness. Puroindolines are endosperm-specific proteins found in wheat and its relatives. In wheat, puroindoline sequence variation controls the majority of wheat grain texture variation. Hordoindolines, the puroindoline homologs of barley, have been identified and mapped. Recently, substantial allelic variation was found for hordoindolines among commercial barley cultivars. Our objective was to determine the influence of hordoindoline allelic variation upon grain hardness and dry matter digestibility in the 'Steptoe' x 'Morex' mapping population. This population is segregating for hordoindoline allele type, which was measured by a HinA/HinB/Gsp composite marker. One-hundred and fifty lines of the 'Steptoe' x 'Morex' population were grown in a replicated field trial. Grain hardness was estimated by near-infrared reflectance (NIR) and measured using the single kernel characterization system (SKCS). Variation attributable to the HinA/HinB/Gsp locus averaged 5.7 SKCS hardness units (SKCS U). QTL analysis revealed the presence of several areas of the genome associated with grain hardness. The largest QTL mapped to the HinA/HinB/Gsp region on the short arm of chomosome 7 (5H). This QTL explains 22% of the SKCS hardness difference observed in this study. The results indicate that the Hardness locus is present in barley and implicates the hordoindolines in endosperm texture control.

Seeding Rate and Genotype Effect on Agronomic Performance and End-Use Quality of Winter Wheat

Few experiments have studied how seeding rates affect agronomic performance and end-use quality of modern wheat (Triticum aestivum L.) genotypes in the Great Plains. Higher grain yield and better quality grain production requires the use of appropriate seeding rates. During the 1997 and 1998 crop seasons, 20 winter wheat genotypes and experimental lines were evaluated at two locations (four environments) to assess seeding rate and genotype effects on agronomic performance and end-use quality of wheat. Significant differences among environments, seeding rates, and genotypes, and some of their interactions were identified. Lower seeding rates decreased plant population (by 62.3%), grain yield (by 0.8 Mg ha−1), kernel weight (by 1.3 mg kernel−1), flour yield (by 0.8 g/100 g grain), mixing time (by 0.7 min), caused later flowering (by 2 d), and increased flour protein content (by 15 mg g−1) and mixing tolerance (1 unit). Environment × genotype interactions were significant for all the traits except plant population and mixing tolerance. On the basis of the four environments, the seeding rate × genotype interactions were nonsignificant for all traits except plant height. These results provide evidence that agronomic performance and end-use quality traits are greatly influenced by the environmental conditions and less so by seeding rates. Seeding rate affected plant population, days to flowering, plant height, grain yield, kernel weight, flour yield, flour protein, and mixing time and tolerance of wheat; therefore, seeding rate should be considered as a factor in obtaining higher grain yields with good end-use quality.

Quality (End-Use) Improvement in Wheat

Abstract Wheat provides nutrients and the raw materials for industrialized food production. Recent global economic trends and increases in urban population growth have led to an increased demand for wheat-based convenience foods (fast, ready-to-eat, frozen foods, etc.) and for new wheat-based products. These factors have resulted in a greater emphasis than ever on the end-use quality of wheat. This paper reviews grain compositional aspects influencing the processing and quality attributes of the main foods produced with wheat, as well as the breeding strategies and methodologies used to achieve germplasm with desirable end-use quality. Common wheat (Triticum aestivum) is used in bread (leavened, flat, and steamed), noodles, biscuits, and cakes. Durum wheat (T. turgidum L. var. durum) is used globally in alimentary pasta and regional foods (flat breads, couscous, and burghoul) in North Africa and West Asia. Grain characteristics (grain hardness, protein content/quality, enzymatic activity, etc.) play a moderate to important role in the processing and end-use quality of wheat-based products. Among these, gluten strength and extensibility, which are determined by glutenin (HMW and LMW) and gliadin composition, are two of the main factors that determine quality. The complex and generally additive nature of inheritance of most quality traits has led to the development of several indirect tests used in early and advanced generations to increase the frequency of high yielding lines with desirable quality attributes. Additionally, characterization of HMW and LMW glutenins and gliadins allows breeders to combine protein content and quality more effectively. The use of molecular-marker-assisted selection and genetic transformation is expected to accelerate the tailoring of new wheat varieties to meet specific end-use quality requirements. Accumulating desirable quality genes will help reduce genotype X environment effects on quality-presently among the major challenges confronting breeders.

Assessing genotypic softness in single wheat kernels using starch granule-associated friabilin as a biochemical marker

The end-use quality of wheat (Triticum aestivum L.) is determined in large part by the texture of the grain (soft or hard). Endosperm texture is currently determined by several empirical methods. These methods are limited because the use bulk grain lots, as opposed to individual kernels; assess phenotypic, as opposed to genotypic hardness; require a quantity of grain greater than that generally available in the early generations of wheat breeding programs, and are destructive. Recent approaches that use single kernels address the problems associated with bulk grain lots, but suffer the other limitations of providing only the phenotype and being destructive. An objective method for determining the texture genotype of single kernels of wheat was developed using starch granule-associated friabilin, a family of closely related 15 kDa proteins, as a biochemical marker. The occurrence of friabilin on water-washed wheat starch granules is apparently unaffected by the environment and is perfectly correlated (no exceptions) with grain softness. The technique presented here can detect friabilin on as little as 0.2 mg of starch and provides a 250-fold improvement in friabilin detection compared to previous methods. The method is capable of correctly assessing the genotype of F1 heterozygotes from hard x soft and soft x hard crosses. Further, the method uses only a portion of the endosperm from the kernel and therefore accommodates embryo propagation and high molecular weight glutenin subunit characterization. This single kernel method also facilitates the genetic characterization of mixed, bulk grain lots.

Use of recombinant inbred lines of wheat for study of associations of high-molecular-weight glutenin subunit alleles to quantitative traits

Recombinant inbred lines (RILs) derived by single plant descent to F8 from a hybrid of Anza, a low-quality cultivar, and Cajeme 71, a high-quality cultivar, differed in alleles at three high-molecular-weight glutenin (HMW-glu) seed storage protein loci. The 48 RILs were classified by SDS-PAGE for the Anza alleles Glu-Alc (null), Glu-B1b (subunits 7 + 8), and Glu-D1a (subunits 2 + 12) and for Cajeme 71 alleles Glu-A1a (sub-unit 1), Glu-B1I (subunits 17 + 18), and Glu-D1d (subunits 5 + 10). All RILs and parents were grown in a replicated field trial with three levels of nitrogen (N) fertilization. Additive and additive x additive gene effects for the three loci were detected by orthogonal comparisons of means for each of six wheat end-use quality traits. Each HMW-glu genotype was represented by three to ten RILs so that variability among RILs within each HMW-glu genotype could be examined. N effects were consistently small. All traits except flour yield were highly correlated with predictor traits studied earlier. Flour protein content, baking water absorption, dough mixing time, bread loaf volume, and bread loaf crumb score were all correlated, suggesting similar gene control for these traits; however, specific additive locus contributions were evident: αB for flour yield; αB and αD for flour protein; and αB for absorption, but differing in sign; all three loci for mixing time, but αB was negative; and all three loci were positively associated with loaf volume. Digenic epistatic effects were significant for flour yield (αAD), flour protein (αAB), and absorption and mixing time (αAD, αBD). Only flour yield showed a trigenic epistatic effect. Six of seven epistatic effects were negative, thus showing how progress in breeding for high quality may be impeded by interaction of genes which, by themselves, have strong positive additive effects. Considerable genetic variance among RILs within a HMW-glu genotype was detected for all traits, and the summation of α effects accounted for a mean of 13% of the parental differences for the six traits examined in this study. Clearly, further resolution of the genetics of wheat quality would be desirable from a plant breeding point of view.

Involvement of a Novel Peptide in the Heat Shock Response of Australian Wheats

A low molecular weight peptide, induced by exposure of coleoptiles to heat stress at 41°C, has been detected by reversed-phase high performance liquid chromatography of extracts from coleoptiles of five wheat (Triticum aestivum) cultivars. This component is detected within 1 h of a 41°C heat shock, is not detected 48 h after cessation of the heat shock, and remains present during a continuous 24 h heat treatment. The appearance of this component is also induced by exposure of the coleoptile to 0.1 M sodium arsenite or 10% ethanol. When other species such as barley (Hordeum vulgare), soybean (Glycine max), sorghum (Sorghum bicolor), maize (Zea mays), mungbean (Vigna radiata), or rice (Oryza sativa) were examined for the presence of a component eluting in the same position, it was only detected in maize. The amino acid sequence for the heat-induced peptide from wheat was determined to be: V-L-V-P-V-P-Q-L-Q-P-Q-N-Q-P/Q. The sequence of 12 of these amino acids is the same as the N-terminal sequence of α- and β gliadins (wheat endosperm storage proteins). The production of this heat-induced peptide in aneuploids of Chinese spring wheat indicated that the peptide gene was located on the same chromosome arm as one of the gliadin genes. The presence of this gliadin-like peptide in heat-stressed coleoptiles may be due to the presence of five heat shock elements in the gene sequence of gliadins. The potential heat inducibility of the gliadin gene has important implications for end-use quality of wheat. The results also imply that seed proteins may have a function other than storage of nitrogen.

MONOCLONAL ANTIBODIES IN AGRICULTURAL TESTING: QUANTITATION OF SPECIFIC WHEAT GLIADINS AFFECTED BY SULFUR DEFICIENCY

Proteins correlating with end-use quality in wheat (Triticum aestivum L.) flour samples have been quantitated using a panel of monoclonal antibodies (MCA) with specificities for different gliadins (grain endosperm storage proteins which are soluble in aqueous alcohol). A beta-gliadin specific antibody was found suitable for measuring sulfur-related quality loss in sets of flours from three wheat cultivars grown under varying conditions of sulfur fertilization. Binding of this monoclonal antibody, measured in a competitive enzyme-immunoassay, was highly correlated with flour sulfur and with the extensibility of, and resistance to stretching of doughs prepared from these flour samples. These results demonstrate that monoclonal antibodies may be used to measure levels of specific components which vary as the technological quality of the foodstuff varies. Rapid spot-tests based on the reaction of seed proteins with specific monoclonal antibodies may aid progeny selection in plant breeding programs.Key words: Wheat-grain quality, monoclonal antibody, immunoassay, sulfur deficiency, gliadin