Marianna Rakszegi

Genetics of dietary fibre in bread wheat

Arabinoxylans (AX) are major components of cell walls in wheat endosperm. The water-extractable part, WEAX, is considered as dietary fibres with health promoting effects. AX exhibit large natural variations in their amount but few studies have been carried out on the genetics of WEAX content and structure in bread wheat. We first carried out a “forward” quantitative genetic approach, using two recombinant populations derived from crosses between WEAX-high and WEAX-low parents and the viscosity of flour extract (WEAX-viscosity) as a predictor of WEAX content. This allowed us to identify two QTL regions, one of them, found on chromosome 6B in both populations, having a major effect with as much as 59% of the phenotypic variation explained by a single QTL. Then, we focused on key enzymes involved in the biosynthetic pathway of arabinoxylans. Out of 34 homoeologous candidate genes studied by sequencing a set of 46 lines, representing a worldwide diversity179 show no polymorphism. In the 16 polymorphic candidate genes, 80 SNP (in 15 genes) and 16 indels (in 4 genes) were detected. Then 27 SNP (in 13 genes) were genotyped in a larger collection of 156 lines (Healthgrain diversity screen). Eight associations were significant at an indicative 5% threshold, but only one, between COMT (Caffeic acid O methyltransferase) on chromosome 7A and A/X in WEAX was significant at a 1% level. The usefulness of these approaches and preliminary results for breeding is discussed.

Diversity of agronomic and morphological traits in a mutant population of bread wheat studied in the Healthgrain program

A mutant population of spring wheat cv. Cadenza was produced at Rothamsted Research in 2004–5, both for TILLING and to generate variation in the contents of phytochemical components studied in the Healthgrain program. The agronomic and morphological properties of this mutant hexaploid wheat population (generations M3–M6) were studied in a 3-year field experiment. Most of the traits were scored according to UPOV TG/3/11, namely the time of ear emergence, plant height, ear glaucosity, shape, density and length, presence of awns and scurs, seasonal type, and grain colour. Other characters such as visible mutant phenotypes, ear sterility, heterogeneity of head rows, leaf colour and responses to powdery mildew and leaf rust were also studied. Variation in certain breadmaking quality parameters was also studied. The EMS mutant Cadenza lines studied showed wide diversity in terms of morphological and agronomic properties. The variation in agronomic properties was lower in 2007 and 2008 than in 2006, partly because of the SSD (single seed descent) in the M4 generation and partly because of the loss of late heading genotypes. The diversity was lowest in 2007, probably due to the extremely dry weather.

Effect of heat and drought stress on the structure and composition of arabinoxylan and β-glucan in wheat grain

The effects of heat (H), drought (D) and H+D (from 12th day after heading for 15 days) on the dietary fiber content and composition (arabinoxylan (AX) and β-glucan) of three winter wheat varieties (Plainsman V, Mv Magma and Fatima 2) were determined. Results showed that H and D stress decreased the TKW, the β-glucan contents of the seeds and the quantity of the DP3+DP4 units, while the protein and AX contents increased. The highest amounts of AX and proteins were in the H+D stressed samples with heat stress also increasing the water extractability (WE) of the AX. However, while the content of AX content was generally increased by all stresses, drought stress had negative effect on the AX content of the drought tolerant Plainsman V. Fatima 2 behaved similarly to Plainsman V as regards to its drought tolerance, but was very sensitive to heat stress, while Mv Magma was the most resistant to heat stress.

1H‐NMR screening for the high‐throughput determination of genotype and environmental effects on the content of asparagine in wheat grain

Summary Free asparagine in cereals is known to be the precursor of acrylamide, a neurotoxic and carcinogenic product formed during cooking processes. Thus, the development of crops with lower asparagine is of considerable interest to growers and the food industry. In this study, we describe the development and application of a rapid 1H‐NMR‐based analysis of cereal flour, that is, suitable for quantifying asparagine levels, and hence acrylamide‐forming potential, across large numbers of samples. The screen was applied to flour samples from 150 bread wheats grown at a single site in 2005, providing the largest sample set to date. Additionally, screening of 26 selected cultivars grown for two further years in the same location and in three additional European locations in the third year (2007) provided six widely different environments to allow estimation of the environmental (E) and G x E effects on asparagine levels. Asparagine concentrations in the 150 genotypes ranged from 0.32 to 1.56 mg/g dry matter in wholemeal wheat flours. Asparagine levels were correlated with plant height and therefore, due to recent breeding activities to produce semi‐dwarf varieties, a negative relationship with the year of registration of the cultivar was also observed. The multisite study indicated that only 13% of the observed variation in asparagine levels was heritable, whilst the environmental contribution was 36% and the GxE component was 43%. Thus, compared to some other phenotypic traits, breeding for low asparagine wheats presents a difficult challenge.

Differentially penalized regression to predict agronomic traits from metabolites and markers in wheat

BackgroundGenomic prediction of agronomic traits as targets for selection in plant breeding programmes is increasingly common. The methods employed can also be applied to predict traits from other sources of covariates, such as metabolomics. However, prediction combining sets of covariates can be less accurate than using the best of the individual sets.ResultsWe describe a method, termed Differentially Penalized Regression (DiPR), which uses standard ridge regression software to combine sets of covariates while applying independent penalties to each. In a dataset of wheat varieties, field traits are better predicted, on average, by seed metabolites than by genetic markers, but DiPR using both sets of predictors is best.ConclusionDiPR is a simple and accessible method of using existing software to combine multiple sets of covariates in trait prediction when there are more predictors than observations and the contribution to accuracy from each set differs.

Micronutrient contents and nutritional values of commercial wheat flours and flours of field-grown wheat varieties-A survey in Hungary

Wheat-based food has great importance in human nutrition: in European countries they provide 20–30% of the daily calorie intake, and additionally, the wholemeal and healthy food becomes even more popular. Mineral content in grains is dependent on genetic and environmental factors (varieties, soil type, geographical location of the growing area, etc.), therefore, it is complicated to estimate how many percentage of the daily micronutrient requirements can be covered by wheat-based products. In this study, copper (Cu), iron (Fe), manganese (Mn), molybdenum (Mo), selenium (Se) and zinc (Zn) contents of 13 commercial wheat flour products, and the white flour and wholemeal of 24 winter type bread wheat varieties were studied to estimate the nutritional value of these products. All investigated samples were produced in Hungary. Significant variation was revealed in the case of all mineral elements in the different brands of wheat flours. Generally, the white flour enriched with germ showed higher mineral contents than the average values of normal white flours. Furthermore, the wholemeal has higher Cu, Fe, Mn and Zn, but not higher Se contents than the white flours. Mo content was also higher in some brands of white flour than in wholemeal. The investigated winter wheat varieties showed significant differences in the case of Fe, Mn, Se and Zn contents, but none of the varieties showed outstandingly high micronutrient content. The milling process – as it was expected – reduces the concentrations of four elements (Fe 33%; Mn 88%; Zn 71%; Cu 44%); however, the Se and Mo concentrations were not affected significantly. Using the average micronutrient content in the wholemeal of varieties, the daily Mn and Fe requirement can be covered by the consumption of about 250 g wholemeal. Additionally, the daily Mo requirement could be met by the daily consumption of 140-190 g of commercial white or wholemeal flour.

Addition of Aegilops U and M Chromosomes Affects Protein and Dietary Fiber Content of Wholemeal Wheat Flour

Cereal grain fiber is an important health-promoting component in the human diet. One option to improve dietary fiber content and composition in wheat is to introduce genes from its wild relatives Aegilops biuncialis and Aegilops geniculata. This study showed that the addition of chromosomes 2Ug, 4Ug, 5Ug, 7Ug, 2Mg, 5Mg, and 7Mg of Ae. geniculata and 3Ub, 2Mb, 3Mb, and 7Mb of Ae. biuncialis into bread wheat increased the seed protein content. Chromosomes 1Ug and 1Mg increased the proportion of polymeric glutenin proteins, while the addition of chromosomes 1Ub and 6Ub led to its decrease. Both Aegilops species had higher proportions of β-glucan compared to arabinoxylan (AX) than wheat lines, and elevated β-glucan content was also observed in wheat chromosome addition lines 5U, 7U, and 7M. The AX content in wheat was increased by the addition of chromosomes 5Ug, 7Ug, and 1Ub while water-soluble AX was increased by the addition of chromosomes 5U, 5M, and 7M, and to a lesser extent by chromosomes 3, 4, 6Ug, and 2Mb. Chromosomes 5Ug and 7Mb also affected the structure of wheat AX, as shown by the pattern of oligosaccharides released by digestion with endoxylanase. These results will help to map genomic regions responsible for edible fiber content in Aegilops and will contribute to the efficient transfer of wild alleles in introgression breeding programs to obtain wheat varieties with improved health benefits. Key Message: Addition of Aegilops U- and M-genome chromosomes 5 and 7 improves seed protein and fiber content and composition in wheat.

Rheological Hardness Index for Assessing Hardness of Hexaploids and Durums

ABSTRACT Kernel hardness of cereal grains is a fundamental phenotype, and various protocols for its characterization have been proposed. Although, from different perspectives, each has proved useful, these methods do not directly address the rheological (fracturing) response of a grain when subjected to compression. Such information is hidden in the individual crush response profiles (iCRPs) obtained by measuring the response of individual grains to crushing on an SKCS 4100 device. Here, the appropriateness and utility of rheological phenotypes, based on single-kernel measurements, are demonstrated by proposing and validating a new wheat grain hardness phenotype, the rheological hardness index (RHI). It is defined in terms of the rheological phenotype phases (RPPs) of the averaged CRPs (aCRPs) obtained by averaging a large number of iCRPs. The utility of RHI is illustrated by showing how it provides improved insight about the differences in brittleness and compactness of grains from different wheat variet...

Selection of winter durum genotypes grown under conventional and organic conditions in different European regions

Quality and agronomic performance of 14 winter durum wheat genotypes (Gs) were examined in Austria, France and Hungary for 3 years. Heading time, wet gluten content, semolina yield and grain protein content are traits that showed G-dependent significant differences between the two management (M) systems examined (conventional and organic). Therefore, breeding for these traits could result in specifically adapted Gs for organic agriculture in different countries. Based on strong or moderately significant correlations between traits, gluten index and plant height could also be specifically selected in an indirect way. The need for environmentally specific selection for grain yield (GY) in later generations was also demonstrated. In general, varieties that had the highest performance in a given mega-environment (E) originated from that mega-E (except for yellow index). This finding provides evidence for the influence of the selection E, whether it is the M system or the growing region. As the French site fell into a distinct mega-E, it should be handled separately. The Hungarian site was found to be an ideal test E for selecting Gs with high adaptability for most of the quality traits, while the Austrian site could be used in selecting agronomic traits. This was also reflected in the breeding origin of the best winter durum Gs for each trait. Based on these findings, a partly separate winter durum selection program is recommended for organic and low input agriculture in each country. As a consequence, specific varieties adapted to sub-optimal growing conditions would support the emerging movement towards sustainable farming systems.

Dataset on the mean, standard deviation, broad-sense heritability and stability of wheat quality bred in three different ways and grown under organic and low-input conventional systems.

An assessment was previously made of the effects of organic and low-input field management systems on the physical, grain compositional and processing quality of wheat and on the performance of varieties developed using different breeding methods (“Comparison of quality parameters of wheat varieties with different breeding origin under organic and low-input conventional conditions” [1]). Here, accompanying data are provided on the performance and stability analysis of the genotypes using the coefficient of variation and the ‘ranking’ and ‘which-won-where’ plots of GGE biplot analysis for the most important quality traits. Broad-sense heritability was also evaluated and is given for the most important physical and quality properties of the seed in organic and low-input management systems, while mean values and standard deviation of the studied properties are presented separately for organic and low-input fields.