Rozprawy doktorskie na temat „Wheat sprouting”

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.

Doctor of Philosophy<br>Department of Agronomy<br>Guihua Bai<br>Guorong Zhang<br>Wheat yield and quality is influenced by many abiotic and biotic environmental factors. Pre-harvest sprouting (PHS) occurs when physiologically matured spikes are exposed to wet field conditions before harvest, which results in seed germination and causes significant losses in yield and end-use quality. Wheat stripe rust is one of the most important biotic factors reducing grain yield and quality. To investigate the genetic basis of the resistance to PHS and stripe rust in hard white winter wheat cultivars Danby and Tiger and develop molecular markers for marker- assisted breeding, a double haploid (DH) population, derived from those two cultivars, was genotyped with simple sequence repeats (SSR) markers and simple nucleotide polymorphism (SNP) markers. This DH population was assessed for resistance to PHS and stripe rust in both greenhouse and field experiments. For PHS, one major resistant quantitative trait locus (QTL) was consistently detected on the short arm of chromosome 3A in all three experiments conducted and explained 21.6% to 41.0% of the phenotypic variation (PVE). This QTL is corresponding to a previously cloned gene, TaPHS1. A SNP in the promoter of TaPHS1 co- segregated with PHS resistance in this mapping population. Meanwhile, two other QTLs, Qphs.hwwg-3B.1 and Qphs.hwwg-5A.1, were consistently detected on the chromosome arms 3BS and 5AL in two experiments. These two QTLs showed significant additive effects with TaPHS1 in improving PHS resistance. For stripe rust, three major QTLs were consistently detected in four out of six environments for infection type (IT) or disease severity (DS). Two of them, QYr.hwwg-2AS1 and QYr.hwwg-4BL1, contributed by the Danby allele explained up to 28.4% of PVE for IT and 60.5% of PVE for DS. The third QTL, QYr.hwwg-3BS1, contributed by the Tiger allele, had PVE values up to 14.7% for IT and 22.9% for DS. QYr.hwwg-2AS1 and QYr.hwwg- 4BL1 are likely the same resistance genes reported previously on chromosome arms 2AS and 4BL. However, QYr.hwwg-3BS1 might be different from the reported gene cluster near the distal end of 3BS where Yr57, Yr4, Yr30 and Sr2 were located. Significant additive effects on reducing IT and DS were observed among these three major QTLs. In order to pyramid multiple QTLs in breeding, user-friendly Kompetitive allele specific PCR (KASP) markers were successfully developed for several QTLs identified in this study. The QTLs and their interactions found in this study together with those novel flanking KASP markers developed will be useful not only for understanding genetic mechanisms of PHS and stripe rust resistance but also for marker- assisted breeding to improve wheat resistance to PHS and stripe rust by gene pyramiding.

Pre-harvest sprouting (PHS) and Pre-maturity amylase (PMA) are physiological defects in wheat grains that reduce their end-use quality. PHS is the precocious germination of grains before harvest while PMA is the accumulation of α-amylase in grains. Both traits are quantitative in their expression and are strongly influenced by the environment. In this project, I studied six Quantitative Trait Loci (QTL) located on chromosomes 1A, 2D, 3A (2 loci), 4A and 7B, which confer resistance to PHS or PMA in UK wheat varieties. The aims of this project were to validate and characterise the effects of these QTL, as well as to fine-map the QTL with the most significant effect. To achieve these aims, isogenic materials were developed to independently study these QTL effects. Physiological characterisation of these QTL showed that they exert their effects by affecting the dynamic of dormancy loss in grains, albeit at different stages of grain development and maturation. We also show that temperature during grain development and germination affect the expression of these QTL effects. In addition to the characterisation above, I also undertook the fine-mapping and positional cloning of the 4A QTL (named Phs), as this QTL showed the highest effect on PHS resistance of all the QTL studied. I took advantage of recent advances in wheat genomics, high-throughput genotyping and the syntenic relationship between wheat and other grasses, to delimit Phs to a less than 0.2 cM interval. Furthermore, examination of the physical map of this interval identified 17 genes with varied biological functions. High-resolution fine-mapping of the 0.2 cM interval in three independent and diverse populations further delimited Phs to a 10 kb genomic interval. Finally, I report on the comparative sequence analysis around this critical interval, and show the presence of some genomic lesions that could be critical for the Phs effect.

High pre-harvest rainfall in 2006 caused significant pre-harvest sprouting (PHS) and weathering throughout the mid-Atlantic soft red winter wheat (SRWW) (Triticum aestivum L.) growing region. Sprouting and weathering caused decreased flour quality due to lowered dough viscosity and decreased ability to withstand mixing and processing for baked goods. Due to its decreased quality, severely sprouted grain is sold for feed, at a lower price per bushel. Pre-harvest sprouting negatively affects the chain of production from the field to baking operations. The purpose of this research was to evaluate the inherent dormancy and PHS resistance, of current SRWW cultivars and to assess the relationship between falling number and flour quality after grain weathering. Employing a weighted germination index (WGI), a large range in dormancy was observed across SRWW cultivars and seed production. Artificial weathering tests confirmed the use of WGI as a tool for screening for dormancy of SRWW cultivars. The WGI consistently identified cultivars with significantly higher or lower inherent dormancy. â Coker 9553â was highly dormant and resistant to PHS. This cultivar maintained an average falling number of 300 seconds even after receiving an average of 215 mm of rainfall, while the mean falling number for all SRWW cultivars after this amount of weathering was 131 seconds. After only moderate weathering, nine of 15 SRWW cultivars in the study exhibited severe sprouting, demonstrating the need for increased PHS resistance in SRWW wheat. Pre-harvest sprouting resistance groupings, based on average 2008 cultivar falling number were accurately predicted by WGI at both 10 (R2=0.79) and 30°C (R2=0.72) No consistent relationship was observed between head angle, glume tenacity or awn length and PHS resistance. Water absorption, dough stability, farinograph arrival and departure times, peak, and 20-minute drop were measured from grain samples with varying degrees of weathering. All parameters were negatively affected by weathering in 2008. Flour quality parameters were more affected by genotype than falling number suggesting that falling number should not be used as the sole indicator of flour quality after grain weathering. It is clear that there are vast differences in dormancy levels and PHS resistance among SRWW cultivars and stronger dormancy and higher resistance to PHS does not automatically ensure higher quality flour.<br>Master of Science

Pre-harvest sprouting in wheat costs farmers millions of dollars every year. Pre-harvest sprouting tolerance (PST) has minimized this problem, but improvement of PST is still necessary. Synthetic hexaploid wheats (synthetics) have been used as sources of genes coding for many useful traits. Two studies evaluated the PST of a synthetic (Altar 84/Aegilops tauschii) and investigated its potential as a source of PST in crosses with wheat cultivars. The first study compared the synthetic with selected wheat checks for PST and with its parent Altar 84 for the germination response of these genotypes to controlled wetting treatments applied to field-grown intact spikes and threshed seed. Spikes were rolled in wet germination paper and the percentages of germinated seed were determined after seven days. Threshed seeds in Petri dishes were wetted with water and vegetative floral tissues (chaff) extracts. Germinating seeds were counted daily for 14 days. The synthetic was more tolerant than Altar 84 and was classified as moderately sensitive. The improved PST of the synthetic over Altar 84 was attributed to Aegilops tauschii. Seed dormancy and water-soluble substances in the chaff of the synthetic and other genotypes appeared to contribute to their PST. The second study used random inbred F��� lines obtained from single and backcrosses between the synthetic (red-seeded) and the sensitive wheat cultivars Opata F��� (red-seeded) and Bacanora 88 (white-seeded). Seed coat color and germination responses of the F5 lines subjected to a five-day spike wetting treatment were evaluated. Pre-harvest sprouting tolerance was moderately to highly inheritable and largely controlled by additive gene effects in the studied populations. An association between red seed coat color and PST was observed but white recombinant lines more tolerant than their sensitive parent were obtained. The synthetic can be used to improve wheats with red and white seed coats. The potential use of the synthetic as a PST source was discussed and a breeding strategy suggested.<br>Graduation date: 1999

Wheat is the world’s third largest food crop, and is relied upon as a food source by millions of people. Securing the supply of wheat is a problem because it is susceptible to many biotic and abiotic factors that limit production. One such factor, sprouting of the grain in the head, because of untimely rainfall prior to harvest, is a substantial problem worldwide. Pre-harvest sprouting has a significant impact on wheat growers, who suffer considerable economic hardship as a result of yield loss during harvesting and subsequent downgrading of their sprouted crops. Wheat processors are also affected by this problem, because sprouted grain has significantly altered chemical properties, making it unsuitable for its intended purpose, and often rendering it suitable for animal consumption only. This study investigated mechanisms of dormancy, in the diploid wheat Triticum tauschii (Coss.) Schmalh., to assess their suitability for use in hexaploid (bread) wheat to prevent pre-harvest sprouting. A soluble germination inhibitor was found in the bracts (palea, lemma and glumes) surrounding the grain of T. tauschii. Fractionation of an aqueous extract from the bracts, by HPLC, identified vanillic acid as being likely to be involved in this inhibition. Further analysis of the extract also identified a strong anti-oxidant capacity, indicating that part of the inhibition of germination may arise from the prevention of oxygen reaching the embryo.

Title page, contents and abstract only. The complete thesis in print form is available from the University of Adelaide Library.<br>Pre-harvest sprouting (PHS) is an important economic problem which affects a significant proportion of the Australian wheat crop through quality downgrading. Grain dormancy is the most effective means of overcoming germination in the wheat spikelet at harvest maturity. It has been a consistent observation over a long period of time that dormant red-grained wheat genotypes are almost more dormant than dormant white-grained genotypes. In white-grained wheat, there are two factors which contribute to dormancy, embryo sensitivity to abscisic acid (ABA) and an interacting and unknown seed coat factor. The proposed dormancy model is that complete dormancy can only be achieved with the coordinate expression of these two factors. This primary objective of this project was to determine the role of this putative seed coat factor in grain dormancy of white-grained wheat."--Abstract.<br>http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1259900<br>Thesis (Ph.D.) -- University of Adelaide, School of Agriculture, Food and Wine, 2006

In this study sprouting two different wheat cultivars under various environmental conditions revealed that varietal variation is the most important factor affecting α-amylase quantity as well as quality to modify flour functionality significantly, followed by pre-soaking duration and temperature. Sprouted wheat flour post five days germination was utilized at different rates to prepare 100 g composite breads. There was an improvement in baking quality and shelf life of breads containing 1% and 5% sprouted flour resulting in a significantly increased loaf volume, better texture, and less retrogradation during 7 days post baking than the control. This study presents opportunities for industry to fortify baked products with sprouted wheat flour to yield functional whole grain products that are nutrient dense and naturally shelf-stable.<br>MITACS

Wheat grain quality is defined by several parameters, of which insect and fungal damage and sprouting are considered important degrading factors. At present, Canadian wheat is inspected and graded manually by Canadian Grain Commission (CGC) inspectors at grain handling facilities or in the CGC laboratories. Visual inspection methods are time consuming, less efficient, subjective, and require experienced personnel. Therefore, an alternative, rapid, objective, accurate, and cost effective technique is needed for grain quality monitoring in real-time which can potentially assist or replace the manual inspection process. Insect-damaged wheat samples by the species of rice weevil (Sitophilus oryzae), lesser grain borer (Rhyzopertha dominica), rusty grain beetle (Cryptolestes ferrugineus), and red flour beetle (Tribolium castaneum); fungal-damaged wheat samples by the species of storage fungi namely Penicillium spp., Aspergillus glaucus, and Aspergillus niger; and artificially sprouted wheat kernels were obtained from the Cereal Research Centre (CRC), Agriculture and Agri-Food Canada, Winnipeg, Canada. Field damaged sprouted (midge-damaged) wheat kernels were procured from five growing locations across western Canada. Healthy and damaged wheat kernels were imaged using a long-wave near-infrared (LWNIR) and a short-wave near-infrared (SWNIR) hypersprctral imaging systems and an area scan color camera. The acquired images were stored for processing, feature extraction, and algorithm development. The LWNIR classified 85-100% healthy and insect-damaged, 95-100% healthy and fungal-infected, and 85-100% healthy and sprouted/midge-damaged kernels. The SWNIR classified 92.7-100%, 96-100% and 93.3-98.7% insect, fungal, and midge-damaged kernels, respectively (up to 28% false positive error). Color imaging correctly classified 93.7-99.3%, 98-100% and 94-99.7% insect, fungal, and midge-damaged kernels, respectively (up to 26% false positive error). Combined the SWNIR features with top color image features correctly classified 91-100%, 99-100% and 95-99.3% insect, fungal, and midge- damaged kernels, respectively with only less than 4% false positive error.