Gotowa bibliografia na temat „Wheat sprouting”

Master of Science<br>Department of Grain Science and Industry<br>Rebecca A. Regan<br>A laboratory-scale method for wheat germination was developed and used to compare hard red winter wheat varieties for sprout related attributes, activity, and whole wheat bread baking performance. WB 4458, WB Grainfield, LCS Mint, LCS Wizard, SY Monument, and T158 wheat varieties grown in three Kansas locations were germinated with the developed small-scale germination method and falling number values were compared. Byrd, Tam 204, and T158 were germinated with a scaled-up germination method aimed at generating samples in three falling number ranges of less than 120 seconds (low falling number and highly sprouted), 250±40 seconds (medium falling number), and 350±40 seconds (high falling number and low sprouting). Controls were un-germinated, sound (>400 seconds falling number), samples of each variety. The control whole grain and sprouted wheat was ground into flour. A mixograph was used to determine dough water absorption and mixing time. Whole wheat bread was made to determine bread volume, crumb characteristics, and bread texture. Overall there were few significant differences within each wheat variety for the different levels of germination. The only significant difference observed in all three varieties was that each highly sprouted grain (<120 seconds falling number) produced bread with significantly lower elasticity than the control within each variety, indicating that this level of germination produced a gummier bread. Elasticity was positively correlated with falling number (r=+0.71). A focused analysis on the Byrd variety compared the germinated samples to samples generated with added malted barley to the same falling number ranges. RVA analysis showed the gelatinization profiles for germinated and malted samples were similar within each falling number range. The highly and medium sprouted grain had significantly lower dough water absorption than the malted counterparts for those levels and the medium sprouted grain also had a lower mix time then the malted sample. There were no significant differences in bread volume, crumb characteristics, or bread texture except the highly sprouted grain had significantly lower elasticity than the control and the malted counterpart was not significantly different. In general, this experiment demonstrated that variety and germination conditions are important considerations in sprouting wheat and that whole wheat flour made from a wide range of germination levels produced quality bread that was not different from the control for most of the parameters investigated.

Doctor of Philosophy<br>Department of Agronomy<br>Guihua Bai<br>Allan K. Fritz<br>Wheat pre-harvest sprouting (PHS), germination of physiologically matured grains in a wheat spike before harvesting, can cause significant reduction in grain yield and end-use quality. Many quantitative trait loci (QTL) for PHS resistance have been reported in different sources. To determine the genetic architecture of PHS resistance and its relationship with grain color (GC) in US hard winter wheat, a genome-wide association study (GWAS) on both PHS resistance and GC was conducted using in a panel of 185 U.S. elite breeding lines and cultivars and 90K wheat SNP arrrays. PHS resistance was assessed by evaluating sprouting rates in wheat spikes harvested from both greenhouse and field experiments. Thirteen QTLs for PHS resistance were identified on 11 chromosomes in at least two experiments, and the effects of these QTLs varied among different environments. The common QTLs for PHS resistance and GC were identified on the long arms of the chromosome 3A and 3D, indicating pleiotropic effect of the two QTLs. Significant QTLs were also detected on chromosome arms 3AS and 4AL, which were not related to GC, suggesting that it is possible to improve PHS resistance in white wheat. To identify markers closely linked to the 4AL QTL, genotyping-by-sequencing (GBS) technology was used to analyze a population of recombinant inbred lines (RILs) developed from a cross between two parents, “Tutoumai A” and “Siyang 936”, contrasting in 4AL QTL. Several closely linked GBS SNP markers to the 4AL QTL were identified and some of them were coverted to KASP for marker-assisted breeding. To investigate effects of the two non-GC related QTLs on 3AS and 4AL, both QTLs were transferered from “Tutoumai A” and “AUS1408” into a susceptible US hard winter wheat breeding line, NW97S186, through marker-assisted backcrossing using the gene marker TaPHS1 for 3AS QTL and a tightly linked KASP marker we developed for 4AL QTL. The 3AS QTL (TaPHS1) significantly interacted with environments and genetic backgrounds, whereas 4AL QTL (TaMKK3-A) interacted with environments only. The two QTLs showed additive effects on PHS resistance, indicating pyramiding these two QTLs can increase PHS resistance. To improve breeding selection efficiency, genomic prediction using genome-wide markers and marker-based prediction (MBP) using selected trait-linked markers were conducted in the association panel. Among the four genomic prediction methods evaluated, the ridge regression best linear unbiased prediction (rrBLUP) provides the best prediction among the tested methods (rrBLUP, BayesB, BayesC and BayesC0). However, MBP using 11 significant SNPs identified in the association study provides a better prediction than genomic prediction. Therefore, for traits that are controlled by a few major QTLs, MBP may be more effective than genomic selection.

Each genotype was exposed to controlled PHS conditions for evaluation of susceptibility or tolerance to sprouting, falling number, kernel color, test weight, and yield. The 24 genotypes were grown in replicated trials at three locations over three years, all data subjected to an analysis of variance. Over three years the genotypes were rated for visual PHS using a 1 to 9 scale, with 1 equivalent to no visual PHS and 9 equivalent to maximum visual PHS. The red genotypes exhibited a higher tolerance to PHS than white genotypes with a mean PHS score of 4.46 compared with 5.16 for white genotypes. Not all the white genotypes were equally susceptible to PHS or more susceptible than the red genotypes, suggesting that not all seed dormancy is linked to the kernel color genes.

Pre-maturity <i>alpha</i>-amylase activity (PMAA) in the absence of sprouting is one of four causes of low Hagberg falling number (HFN) in UK winter wheat (<i>Triticum aestivum</i>), reducing the quality and value of milled flour. Other causes include the retention of pericarp <i>alpha</i>-amylase activity (RPAA), pre-maturity sprouting (PrMS) and post-maturity sprouting (PoMS). This thesis investigated the effects of environmental factors on PMAA which currently occurs in a variable and unpredictable fashion under UK weather conditions. A multi-site field experiment on four cultivars (Haven, Hornet, Pastiche and Riband), at four sites (Harper Adams University College, University of Nottingham, University of Aberdeen and ADAS-Bridgets) between 1994-1996 was undertaken to:- establish the frequency of the causes of low HFN; examine the relationship between grain drying-rate and PMAA; determine if it was possible to predict combine harvest HFN. A range of techniques including a visual sprouting assessment, fluorescein dibutyrate staining, iso-electric focusing and a beta-limit dextrin gel and iodine staining test were used to allow the cause of low HFN to be established. Of the forty crops analysed, 22 cases (45%) had detectable amounts of <i>alpha</i>-amylase activity. PMAA was identified solely in 2 cases (5%), in combination with PoMS in 8 cases (20%), in combination with RPAA in one case (2%), with PoMS occurring solely in 11 cases (28%). The HFN fell below the breadmaking standard of 250 s in 18 of the 36 site x year x cultivar combinations analysed. This was attributed solely to PMAA in two cases (11 %), a combination of PMAA and PoMS in a further eight cases (44%) and solely to PoMS in eight cases(44%). There were no cases where PrMS or RPAA reduced the HFN to below 250 s. The hypothesis that PMAA is related to the grain drying-rate between 40-20 % moisture content was tested. Grain drying-rate was determined by linear regression analysis using moisture content measurements made at regular intervals during grain development. In site x year x cultivar combinations where PMAA was detected the grain drying-rate was significantly (P = 0.047) lower (mean = 1.90 <i>cf</i>. 2.30% moisture loss day^-1), suggesting a slow grain drying-rate enhances PMAA. However, the low frequency of occurrence of PMAA in isolation prevented quantification of this relationship. Initiation of PMAA in the grain, was shown to occur from a grain moisture content of 47.8%. A pre-harvest sample taken by hand at 850 °C-days (35 % moisture, Zadoks growth stage 85-87) was shown to enable a prediction of combine harvest HFN to be made in the absence of subsequent rainfall and PoMS. The 95 % confidence limits associated with this HFN prediction were however wide. The hypothesis that transient changes in temperature early in grain development may affect PMAA, before the onset of any grain drying-rate effects, was tested in five controlled-environment cabinet experiments. Of 36 cultivar x time of transfer combinations undertaken from a 16/ 10°C to a 26 /20°C temperature regime, six led to a significant increase (P < 0.05) arid one led to a significant decrease in PMAA. Of the 18 cultivar x time of transfer combinations undertaken from a 25 / 20°C to a 16 / 10°C temperature regime, one led to a significant increase and one led to a significant decrease in PMAA. A comparison between the field and controlled-environment experiment results highlighted that after conditions putatively stimulating PMAA had been encountered, subsequent environmental factors, such as mean temperature and relative humidity may also affect PMAA. It was concluded that PMAA can be enhanced by transient increases in temperature before the grain reaches 40% moisture content and by a slow grain drying-rate between 40-20% moisture content. The variability in the results, however, also suggested other environmental factors were influencing PMAA.

Wheat and wheat products represent a major food staple consumed around the world. Asian noodles account for the end-use of at least twelve percent of all wheat produced globally. Whereas there has been extensive research into the role and significance of enzymes in the utilisation of wheat flour in bread-making, less is known of their role in Asian noodles. Accordingly, this study has been based on the hypothesis that some enzymes will have a significant impact on the quality characteristics of at least some styles of Asian noodle products. Five enzymes were selected for study: á-amylase, lipase, lipoxygenase, peroxidase and ascorbic acid oxidase. The focus has been on the processing of white salted and yellow alkaline styles of Asian noodles and the role of the enzymes in relation to the quality attributes of these products has been systematically investigated. The quality aspects encompass colour and colour stability, texture, cooking properties as well as structural characteristics of the products. As a part of the preliminary phases of the investigation, procedures for analysis and assessment of flours and noodles have been evaluated. In particular, for the textural properties of noodles, results were obtained with the TA-XT2 Texture Analyser using both a flat cylinder probe, to measure noodle hardness, and also a cutting blade measuring noodle firmness. In addition, various approaches were trialled for sample preparation and presentation in the use of scanning electron microscopy for the investigation of noodle structure. In order to measure the activity of the enzymes in flours and noodle products, assay procedures were set up and validated. These were then used for the analysis of a series of commercial flours and the levels of activity in each of the flours was relatively low indicating that they had been milled from wheat which had not been subjected to preharvest sprouting. á-Amylase was measured using the Ceralpha method and two different sources of exogenous á-amylase (bacterial and barley) were added to noodle formulations. In preliminary experiments various levels of á-amylase incorporation were compared and Abstract viii the impact on texture measured. Both sources of á-amylase resulted in softer noodle products. Adverse effects of the preparations on colour were observed in fresh noodles, although the differences were less obvious when noodles were cooked or dried immediately after preparation. Cooking losses were higher in noodles incorporating amylase, particularly the bacterial preparation. These impacts were reflected in changes in the appearance of starch granules in scanning electron micrographs of the noodles. Three different lipase preparations were studied and their incorporation had only minor effects on texture of noodles. Addition of wheat germ lipase resulted in slightly softer noodles, fungal lipase caused slightly harder noodles, while addition of porcine pancreas lipase gave harder noodles in the raw state and softer noodles after cooking. Similarly variable results were observed when colour and colour stability were evaluated, and there were no adverse effects upon cooking quality of Asian noodles. Two different preparations of horseradish peroxidase were investigated and both resulted in adverse effects on colour including at all stages of storage. One of the preparations resulted in softer noodles when texture was measured using the cylinder method and in firmer noodles when the blade attachment was applied. Neither the surface appearance of noodles nor the cooking properties were altered by the addition of peroxidase to the formulations. Different levels of addition of ascorbic acid oxidase from Cucurbita species showed only minor effects on characteristics for both styles of noodles. Incorporation of this enzyme resulted in lower lightness values but there was little effect on yellowness. Discolouration of noodle sheets was faster and more obvious at 25°C and compared to the storage of noodles at 4°C. The cooking qualities of noodles did not change upon addition of the oxidase. Activity of the enzyme lipoxygenase was measured spectrophotometrically using linoleic acid as substrate. Upon addition to the noodle formulations the enzyme preparation from soy bean resulted in slightly harder and firmer noodles. Colour and colour stability were not enhanced by the addition of lipoxygenase and significantly higher yellowness values were measured in some samples. This enzyme did not adversely impact upon the cooking or structural properties of either style of noodles. Abstract ix Some of the enzymes studied here demonstrated undesirable impacts on one or another aspect of noodle quality, particularly producing darkening or soft textural characteristics. Enzymes that might usefully be considered at lower levels of addition are ascorbic acid oxidase, porcine pancreas lipase and lipoxygenase. These three had no negative effects upon texture, structure or cooking quality of noodles. Visually the colour properties were not adversely impacted and instrumental assessment indicated brighter noodle sheet colours. At lower levels of addition, these three enzymes provide enhancement of noodle quality. On the other hand peroxidase, the two amylases and lipases affected the colour and colour stability of noodles. It was observed that the amylase preparations did result in pronounced softening of noodles. However, the data indicate that the adverse impact attributed to this enzyme when flour from sprouted wheat is used in noodle processing, are probably due to enzyme activities other than a- amylase.

[Truncated abstract] Wheat is the main crop in Australia and there are stringent quality requirements. Preharvest sprouting induced by rainfall between maturity and harvest lowers grain quality from premium to feed grades and reduces yield. Wheat production has expanded into the southern Western Australian region where preharvest sprouting occurs in ~1 in 4 seasons and development of more preharvest sprouting tolerant genotypes is required. The main mechanism for improving preharvest sprouting tolerance is grain dormancy. There is genetic variation for dormancy based in the embryo and seed coat but dormancy is complex and is influenced by environmental conditions during grain filling and maturation. Screening and selecting for preharvest sprouting tolerance is problematic and the level of tolerance needed for regions which differ in the level of dormancy they impose, requires clarification. The research presented here aims to answer the underlying question for breeders of how much dormancy is required for preharvest sprouting tolerance in contrasting target environments of the central and coastal wheat belt regions of Western Australia. In the central and coastal wheat belt regions, field trials with modified environments were used to determine the environmental influence on dormancy. Water supply (without directly wetting the grain) and air temperature were modified during grain development in a range of genotypes with different mechanisms of dormancy to determine the influence of environment on dormancy. ... Genotypes with embryo dormancy were consistently the most preharvest sprouting tolerant, even though this dormancy was influenced by the environmental conditions in the different seasons. Pyramiding the embryo component with the specific seed coat component and/or awnless head trait removed some of the environmental variation in preharvest sprouting tolerance, but this was generally considered excessive to the environmental requirements. The methods developed here, of field imposed stresses may provide a valuable tool to further understand the influence of environment on the regulation of dormancy, as different phenotypes can be made with the same genotype. Moisture stress, sudden changes in water supply or high temperatures during the late dough stages influenced dormancy phenotype and should be considered and avoided if possible when selecting locations and running trials for screening for genetic differences in preharvest sprouting tolerance. In the Western Australian context, the embryo component of dormancy appeared to be sufficient and should be adopted as the most important trait for breeding for preharvest sprouting tolerance.