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1
Dick, G., J. Harper, L. Moore e M. Ottman. "Effect of Russian Wheat Aphid on Durum Wheat Yield". College of Agriculture, University of Arizona (Tucson, AZ), 1988. http://hdl.handle.net/10150/200817.
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2
Zubaidi, Akhmad. "Growth and yield of durum and bread wheat". Title page, contents and summary only, 1996. http://web4.library.adelaide.edu.au/theses/09A/09az93.pdf.
Testo completoAbstract (sommario):
Bibliography: leaves 148-160. A series of experiments was conducted to examine the growth and nutrient uptake of durum and bread wheat at a number of sites in South Australia. The experiments examined response to water stress, the pattern of root and shoot growth, soil water extraction and nutrient uptake among a range of adapted bread wheat and durum wheat cultivars.
3
Husaker, Douglas, e Dale Bucks. "Crop Yield Variability in Irrigated Wheat". College of Agriculture, University of Arizona (Tucson, AZ), 1986. http://hdl.handle.net/10150/200484.
Testo completoAbstract (sommario):
Optimum design and management of irrigated wheat production is limited by the scarcity of information available on yield variability. The purpose of this study was to evaluate the spatial variability in soil-water parameters and the effects compared to grain yield response under level-basin irrigation. Three levels of seasonal irrigation water and two border lengths were used. Grain yields were found to increase significantly with the amount of water applied and soil water depletion (estimate of crop evapotranspiration), although yield variability was greater with reduced or deficit irrigations. Variations in soil water content were responsible for about 22% of the variability in grain yield, indicating that other soil and crop- related factors had a significant influence on production. Spatial dependence was exhibited over a greater distance at the wetter compared with the drier irrigation regimes.
4
Torofder, Golam. "Manipulating wheat yield in semi-arid environments". Thesis, University of Aberdeen, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.394451.
Testo completoAbstract (sommario):
Findings from a number of recent glasshouse studies are reported and their relevance to wheat production practices in Bangladesh is discussed. It was found that application of large amounts of urea gave highest grain yield when the total amount of urea was added immediately after irrigation following germination. The same amount of urea applied before irrigation or in smaller doses throughout the growing season gave lower yield and resulted in higher post-harvest concentrations of soil nitrate. Reducing the total urea application to one quarter of the typical maximum reported value, did not cause a reduction in yield and this could be achieved with only one occasion of irrigation (as opposed to two) following germination. The findings confirm the recommended dosage of urea (typically 250 kg urea ha-1) and indicate the importance of applying urea after irrigation to maximise yield and minimise post-harvest soil nitrate concentrations. Adding a nitrate fertiliser as opposed to the same amount of urea-N did not result in a significant yield increase. The results indicate that application of urea-N following irrigation results in a rapid availability of soil N for plant uptake. Where severe soil drying occurs in the upper rooting zone, grain field was drastically reduced. This occurred even where longer roots had access to non-limiting amounts of water and nutrients. It was found that roots in the drying soil produced the plant hormone abscisic acid (ABA) and that this had a likely causal significance in decreasing yield. ABA was also produced in plants with ammonium- as opposed to nitrate nutrition and this was also associated with reduced yield. It was concluded that breeding for deep rooting alone would be insufficient to attain high yield if the upper part of root system was exposed to severe soil water deficit. Breeding of deep rooting in combination with a decreased sensitivity of stomatal closure to ABA, is an attractive possibility for plant and yield improvement for semi-arid zones. In the interim, current measures of tillage and mulching that enhance the water content of the upper rooting zone should be encouraged. Such measures are likely to counter the potential ABA-induced inhibition of yield associated with partial root dehydration and incomplete nitrification of soil ammonium.
5
Misailidis, Nikiforos. "Understanding and predicting alcohol yield from wheat". Thesis, University of Manchester, 2010. https://www.research.manchester.ac.uk/portal/en/theses/understanding-and-predicting-alcohol-yield-from-wheat(845cbadd-5825-488e-94e7-160c60b2ef0d).html.
Testo completoAbstract (sommario):
Bioethanol is a promising renewable biofuel and wheat is currently the main candidate asthe feedstock for its production in the UK context. The quality of the numerous varieties ofwheat developed in the past by plant breeders has been well examined in terms of bread, biscuitand pasta producing industries. In general, the end-use quality determination of wheat in termsof alcohol yield is less investigated. This work focused on understanding and predicting thealcohol yield from wheat according to its physical, physicochemical and chemicalcharacteristics. The research ran alongside the GREEN Grain project and utilised its wheatsamples, which consist of a range of wheat varieties, agronomic regimes and growing sitesfrom four harvests years 2005-2008. The combined dataset consists of a diverse range ofchemical, physicochemical and physical characteristics of the GREEN Grain wheats. An initial multivariate analysis (PCA) indicated that the first principal component, whichexplains most of the variability of the wheat characteristics, is related with the classification ofwheat as hard or soft. High alcohol yielding wheats typically have high starch, mealiness andalbumin+globulin fraction, and also low protein, gliadin fraction and hardness. They also havelarger and more spherical kernels. Analysis of Variance (ANOVA) was applied in order to identify differences between thevarieties, the sites and the application or not of N fertiliser. The ANOVA showed that theapplication of N fertiliser increases all the protein components, although it increases the Gliadinand the LMW glutenins more. N fertiliser also yields smaller (TGW, width, depth) and moreelongated kernels. High alcohol yielding varieties tend to be softer with lower protein andlarger and more spherical kernels. This consistent variability allowed prediction of the alcoholyield based on easily measured parameters. The following model, based on the SKCS reportedvalues plus protein, could predict the alcohol yield with an R2 of about 78%:Alcohol yield = 466.62 - 5.07 × Protein - 0.21 × hardness + 11.6 × diameter ±6.94 l/dry tonIt is frequently hypothesised that larger and more rounded kernels produce more alcoholbecause they have a smaller relative amount of the unfermentable outer layers. In an effort totest this hypothesis, the pericarp thicknesses and the crease characteristics of the wheat sampleswere measured. It was found that pericarp thickness and crease dimensions vary with kernelsize, with significant differences between varieties. A physical model was developed thatconsiders these differences and calculates the endosperm to non-endosperm ratio. None of thevariables obtained by the physical model could be related to alcohol yield. The SKCS fundamental data were further analysed in an effort to improve the alcoholyield predictability. It was found that the averaged Crush Response Profiles are morereproducible than the hardness index itself. It was shown that the initial peak does not occurbecause of the "shell" (i.e. the bran layers) as suggested in the literature, but because of thecrease. Examination of the effects of moisture content on the aCRPs showed that their 1stquarter is equivalent to the stress-strain plots of dedicated rheological tests. The remaining partsof the curve relate to the post-failure behaviour of the kernels and with hardness as used incereal science. The aCRP parameters could improve the alcohol yield predictability of theGREEN Grain wheats to an R2 of about 82.3% and a standard error of the regression of6.3 l/dry ton. Further standardisation and calibration with respect to the moisture content and tothe size of the kernels could improve the predictions even further. Textural testing of cereals is constrained by the complexity of the wheat kernel structureand exacerbated by the between-kernel variation. The current work has demonstrated howSKCS data can be interpreted more insightfully in order to improve end-use quality predictions. The aCRP parameters clearly contain rheological information about wheats. Further research toestablish their examination by more standardised methodologies will allow effectiveinvestigation of connections between the rheological properties, chemical characteristics,processing behaviour and end-use quality prediction of wheat.
6
Farr, Chuck. "Yield Requirements of Non-Premium Durum Wheat". College of Agriculture, University of Arizona (Tucson, AZ), 1986. http://hdl.handle.net/10150/200542.
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7
Grotenhuis, Timothy P. "Superoptimal CO2 Reduces Seed Yield in Wheat". DigitalCommons@USU, 1996. https://digitalcommons.usu.edu/etd/6747.
Testo completoAbstract (sommario):
Although projected terrestrial CO2 levels will not reach 1000 μmol moI-1 (0.1%) for many decades, CO2 levels in growth chambers and greenhouses routinely exceed that concentration. CO2 levels in life support systems in space can exceed 10,000 μmol moI-1 (1%) CO2. Numerous studies have examined CO2 effects up to 1000 μmol mol-1, but theoretical and some experimental evidence indicates that the beneficial effects of CO2 continue past 1000 μmol mol-1 and are near-optimal for wheat at about 1200 μmol mol-1.
We studied the effects of near-optimal and superoptimal CO2 levels (>1200 μmol mol-1) on yield of two cultivars of hydroponically grown wheat in 12 trials. Increasing CO2 from suboptimal to near-optimal (350 to 1200 μmol mol-1) increased vegetative growth by 25% and seed yield by 15% in both cultivars. Yield increases were primarily the result of an increased number of heads m-2. Further elevation of CO2 to 2500 μmol mol-1reduced seed yield by 22% in cv. 'Veery-10' and by 15% in cv. 'USU-Apogee'. Superoptimal CO2 did not decrease the number of heads m-2, but reduced seeds per head by 10% and mass per seed by 11%. CO2 toxicity occurred over a wide range of light levels. Subsequent trials revealed that superoptimal CO2 in the 2 weeks before and after anthesis mimicked the effect of constant superoptimal CO2. Furthermore, near-optimal CO2 in the 2 weeks before and after anthesis mimicked the effect of constant near-optimal CO2. Nutrient concentration of leaves and heads was not affected by CO2. The yield decreases may be a response mediated by ethylene.
8
Ottman, Michael J. "Wheat and barley varieties for Arizona, 2017". College of Agriculture, University of Arizona (Tucson, AZ), 2017. http://hdl.handle.net/10150/625860.
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9
Ottman, Michael J. "Wheat and barley varieties for Arizona, 2016". College of Agriculture, University of Arizona (Tucson, AZ), 2016. http://hdl.handle.net/10150/625421.
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10
Sloane, David. "Early vigour : its role in enhancing the productivity of wheat grown in South Australia /". Title page, contents and abstract only, 1999. http://web4.library.adelaide.edu.au/theses/09AFP/09afps634.pdf.
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11
Mog, David L. "An analysis of factors influencing wheat flour yield". Thesis, Kansas State University, 2011. http://hdl.handle.net/2097/12452.
Testo completoAbstract (sommario):
Master of AgribusinessDepartment of Agricultural Economics
John A. Fox
The cost of wheat is the largest input cost for a flour mill, and as a result, profitability in wheat flour milling is determined in large part by milling efficiency – i.e., the amount of flour extracted per unit of wheat milled. In this project the objective was to quantify the influence of several measurable variables on flour mill efficiency. Data was collected from two commercial milling units of similar size. Linear regression was then used to estimate the relationship between flour yield and variables measuring grain characteristics and environmental factors. The analysis suggests that increasing ambient temperature and the occurrence of downtime both have a significant negative effect on flour yield. A significant difference in flour yield efficiency was also found between the two mills.
12
Craufurd, P. Q. "Plant development and yield in wheat (Triticum aestivum L.)". Thesis, University of Reading, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.352335.
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13
Alghamdi, Mohammed A. M. "Plant growth regulators effects on vegative growth, yield and yield components in winter wheat". Thesis, University of Reading, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.553077.
Testo completoAbstract (sommario):
Three glasshouse experiments and one field experiment were carried out to investigate the effect of the plant growth regulator on vegetative growth and yield components of reduced height isogenic lines of the wheat (Triticum aestivum L.) cultivar Mercia. The first experiment compared the growth regulator response of seven isogenic lines of Mercia. Subsequent experiments used four lines, (Mercia control, Rhtl Rht2, and Rht8). Two glasshouse experiments examined the responses under well watered and water stress conditions. The third glasshouse experiment examined rates and time of application under well watered conditions, whilst the field experiment had different rates of application. In all experiments growth regulators reduced plant height significantly in all lines. Growth regulator decreased total dry matter and grain yield with greatest reduction generally for the control and Rht8 lines. Rhtl was the least affected. There were few significant effects of growth regulator on gas exchange and chlorophyll fluorescence but the trend was for greater values with growth regulator. In the first glasshouse experiment, a rate of 2.0 1 ha-1 applied just before the third node detectable stage under non water stressed and water stressed conditions gave slight increases in yield of up to 14% except for line Rht10 which increased significantly in non-stressed conditions. In the second glasshouse experiment, a rate of 2.5 1 ha" applied at the start of stem elongation under 30% FC and 100% FC gave reductions in yield up to 16% for the growth regulator and 55% under water stress. In the field experiment, rates of 2.5 and 3.0 1 ha-1 applied at the start of stem elongation gave reductions in yield up to 20% mainly through individual seed weight. In the final glasshouse experiment, rates of 2.5 and 3.0 1 ha-l applied at 6 leaves unfolded and 1st node detectable both reduced grain yield.
14
Green, Andrew Justin. "Yield Improvement in Eastern Soft Red Winter Wheat from 1919 to 2009". Thesis, Virginia Tech, 2011. http://hdl.handle.net/10919/36086.
Testo completoAbstract (sommario):
Periodic evaluation of improvements in yield and disease resistance is necessary to assess breeding progress over time, and the elucidation of underlying traits responsible for yield gains can help direct future breeding. Objectives of this study were: 1) to determine the rate and magnitude of yield progress in eastern soft red winter (SRW) wheat (Triticum aestivum, L.) cultivars released from 1950 to 2009 relative to a historical cultivar Red May (1919) and; 2) to determine effects of leaf rust (Puccinia triticina f. sp. tritici) and powdery mildew [Blumeria graminis (DC.) E.O. Speer f. sp. tritici Em. Marchal] on grain yield components and agronomic traits. Replicated yield trials were grown at Warsaw, VA in 2010 and 2011, and at Holland and Blacksburg, VA in 2011. For objective 1, the genetic progress experiment: flag leaf angle, kernel weight, spikes m-2, lodging, flowering date and harvest index collectively explained the most yield variation in multiple environments on the basis of linear regression analysis. Rate of genetic yield improvement ranged from 0.56% yr-1 at Holland in 2011 to 1.4% yr-1 at Blacksburg in 2011. For objective 2, the disease loss experiment: yield losses ranged from 1% at Holland in 2011 to 21% at Warsaw in 2011. Losses primarily due to powdery mildew and leaf rust were as high as 14% and 33%, respectively. Powdery mildew had the largest negative correlation with harvest index and seeds spike-1, while leaf rust had the largest negative correlation with plant biomass and harvest index.Master of Science
15
Ottman, Michael J., Michael D. Sheedy e Richard W. Ward. "Small Grains Variety Evaluation at Maricopa, 2016". College of Agriculture, University of Arizona (Tucson, AZ), 2016. http://hdl.handle.net/10150/625426.
Testo completoAbstract (sommario):
4 pp.Small grain varieties are evaluated each year by University of Arizona personnel. The purpose of these tests is to characterize varieties in terms of yield and other attributes. Variety performance varies greatly from year to year and several site-years are necessary to adequately characterize the yield potential of a variety. A summary of small grain variety trials conducted by the University of Arizona can be found online at https://extension.arizona.edu/sites/extension.arizona.edu/files/pubs/az1265-2015.pdf.
16
Metho, Lewis Amollo. "Yield and quality response of four wheat cultivars to soil fertility, photoperiod and temperature". Diss., Pretoria : [s.n.], 1999. http://upetd.up.ac.za/thesis/available/etd-10092002-124728.
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17
Landau, Sabine. "A parsimonious model of wheat yield response to environment". Thesis, University of Nottingham, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.389366.
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18
Lintell-Smith, Gail. "The population dynamics of weeds in winter wheat". Thesis, University of East Anglia, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.297011.
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19
Harper, John, e David K. Parsons. "Small Grain Variety Yield Comparisons, Maricopa Agricultural Center". College of Agriculture, University of Arizona (Tucson, AZ), 1985. http://hdl.handle.net/10150/200517.
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20
Zahedi, Morteza. "Physiological aspects of the responses of grain filling to high temperature in wheat". Title page, abstract and contents only, 2001. http://web4.library.adelaide.edu.au/theses/09PH/09phz19.pdf.
Testo completoAbstract (sommario):
"June 2001." Includes bibliographical references (leaves 217-248). The effects of a sustained period of moderately high temperature on physiological and biochemical aspects of grain development were investigated in wheat cultivars grown under controlled environment conditions. The effect of variation in plant nutrition on the responses of cultivars to high temperature was also studied.
21
Shantz, Kim. "1985 Western Plant Breeders Advanced Wheat Yield Trials, Maricopa County". College of Agriculture, University of Arizona (Tucson, AZ), 1985. http://hdl.handle.net/10150/200516.
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22
Wade, James. "Break-even Analysis of Durum Wheat Varieties: Price vs. Yield". College of Agriculture, University of Arizona (Tucson, AZ), 1986. http://hdl.handle.net/10150/200483.
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23
Ottman, Michael J., e Stephen H. Husman. "Irrigation practices and Solum test weight and yield, 2002". College of Agriculture, University of Arizona (Tucson, AZ), 2002. http://hdl.handle.net/10150/203823.
Testo completoAbstract (sommario):
Solum is a barley adapted to one or two irrigations but the grain produced is often low in test weight. Studies were conducted on two commercial farms near Maricopa and Coolidge in an effort to verify data from previous studies suggesting that delaying the first post-emergence irrigation until boot increases test weight compared to earlier irrigation, but does not affect yield. The irrigation treatments consisted of 1) two irrigations – planting and boot, or 2) three irrigations – planting, 5- to 6-leaf stage, and heading (grower standard). The irrigation treatments had no effect on grain yield, test weight, kernel weight, or lodging at either location, but delaying the second irrigation until boot reduced plant height at Coolidge. Despite the lack of positive results from these studies, applying the second irrigation at boot may still be preferable to earlier applications because of reduced plant height and the risk of lodging. We have not been able to measure a benefit from a third irrigation for Solum barley in these or previous studies.
24
Kirigwi, Francis M. "Identification of markers associated with grain yield and components of yield under water stress in wheat /". Search for this dissertation online, 2005. http://wwwlib.umi.com/cr/ksu/main.
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25
Xie, Quan. "Physiological and genetic determination of yield and yield components in a bread wheat × spelt mapping population". Thesis, University of Nottingham, 2015. http://eprints.nottingham.ac.uk/28998/.
Testo completoAbstract (sommario):
A substantial increase in wheat yield is needed for global food security. This requires a comprehensive understanding of the physiological and genetic basis of yield determination. The present study aimed to dissect yield physiologically and genetically in a recombinant inbred line mapping population derived from bread wheat × spelt. A total of 201 traits were investigated in the field and glasshouse across three years, and these traits formed five themes: genetic variation in yield and yield components, and the usefulness of spelt as a genetic resource; tillering dynamics; biomass accumulation; flowering time and subsequent leaf senescence; and grain filling processes. Large genetic variation in all traits was found, and spelt showed many desirable traits and alleles independent of low threshability, so it can be used to broaden genetic diversity for yield improvement in bread wheat, while maintaining the free-threshing habit. Quantitative trait loci for tiller production and survival were identified, which were also affected by light environment under the canopy: low red:far red ratio (R:FR) led to early tillering cessation, few total shoots, high infertile shoot number and shoot abortion, probably resulting from an assimilate shortage due to early and enhanced stem growth induced by low R:FR. More fertile tillers normally contributed to plant yield and grain number, but reduced individual grain weight, partly because of smaller carpels and fewer stem water soluble carbohydrates at anthesis. In addition, preanthesis biomass accumulation increased yield and yield components. For grain weight, slightly early anthesis and delayed but fast leaf senescence were associated with larger grains. Carpel size at anthesis, grain dry matter and water accumulation, as well as grain morphological expansion, determined final grain weight, because of pleiotropy or tight gene linkages. These findings provide deeper insight into yield determination in wheat, and facilitate trait-based physiological and molecular breeding.
26
Popoff, Evan. "An approximate spatio-temporal Bayesian model for Alberta wheat yield". Thesis, University of British Columbia, 2014. http://hdl.handle.net/2429/47033.
Testo completoAbstract (sommario):
Crop forecasting models are very valuable to a number of agricultural and government agencies. We investigated the effect of spatial and temporal environmental climate covariates on the growth of crop yield (wheat) at the regional scale across the province of Alberta. Model fitting was accomplished using data collected during the growing season from climate stations across Alberta provided by Agriculture and Agri-Food Canada (AAFC). A best fitting model was selected which takes into account simplicity (number of covariates used) and accuracy (predictive capability based on two selection criteria).
There have been a number of Bayesian methods for predicting wheat yield. However, many of these methods typically involve extensive algorithms such as a Metropolis-Hastings Markov Chain Monte Carlo (MCMC) that adds substantial computational complexity and run-time. We investigated the application of a spatio-temporal Bayesian model entitled the Integrated Nested Laplace Approximation (INLA). This method offers a computationally cheaper alternative to the MCMC approach and is capable of handling large data requiring interpolation (data sparsity) with relative ease. By structuring the model to have a sparse precision matrix, INLA is able to simplify posterior marginal estimation of the parameters by incorporating the Laplace approximation. The INLA model demonstrated strong predictive capabilities when predicting for one year in advance or hind-casting for a it single previous year. However, when multiple years of data were removed or predictions were made for multiple years in advance, INLA struggled to make predictions which deviated considerably from the mean of the remaining data. Predictive performance in the best fitting model saw a 40% increase in root mean squared error (RMSE) when moving from one year to two and another 6% increase when moving from two to three years. We conclude that the INLA model structure offers valuable information when examining one year in advance but caution should be taken when attempting to forecast for multiple years in advance.
27
Al-Ghzawi, Abdul Latief Ali. "The physiological processes determining grain yield potential in winter wheat". Thesis, University of Nottingham, 2007. http://eprints.nottingham.ac.uk/12885/.
Testo completoAbstract (sommario):
Winter wheat (Triticum aestivum L. ) is the most important crop grown extensively in the UK. There is a gap between yield production and world demand for wheat. So, there is a need to fill this gap. The overall objective of the present study is to investigate the physiological determinants of grain yield potential in winter wheat grown in UK conditions using doubled-haploid lines derived from a cross between winter wheat varieties Rialto and Spark. These varieties are known from previous work to contrast for source and sink type traits and for the presence/absence of the 1 BL/ IRS translocation and the Rht-Dl b semi-dwarf allele. Three field experiments (at Sutton Bonington, University of Nottingham 2003/4, 2004/5 and 2005/6) were conducted examining 25 DH lines of the Rialto x Spark population and the two parents. Two post-anthesis shading treatments (with and without shading) were applied to six genotypes (four DII lines and two parents) in 2003/4 and 2004/5. Two post anthesis de-graining treatments (with and without degraining) were applied to twelve genotypes (ten DH lines and two parents) in 2003/4 and 2004/5. Detailed measurements of grain growth were carried out on the two parents for five pre-determined grain positions within the ear. A range of physiological traits were measured, including developmental stages, light extinction coefficient, radiation interception, radiation-use efficiency (RUE), green area and biomass, stem water-soluble carbohydrate reserves, floret fertility, potential grain weight, grain filling rate and duration, final grain weight and combine grain yield. A source-sink balance model which quantified the source: sink balance during grain growth indicated that the four DH lines and the two parents were sink-limited during grain growth. The sink manipulation treatment (de-graining) generally confirmed the sink limitation in this population although small positive responses of grain growth to de-graining for a few lines indicated they may have been close to source limitation. Radiation-use efficiency measured as the regression slope of dry matter on accumulated PAR intercepted between onset of stem elongation and anthesis differed amongst genotypes in 2004,2005 and 2006. Pre-anthesis RUE was positively correlated with each of grains m2 and specific leaf weight (SLW). The 1BL/IRS translocation increased RUE significantly. The characterisation of the 25 DH lines in this study showed that the differences in grain yield were positively correlated with grains m'2 but not individual grain weight. There was positive correlation between stem WSC reserves and yield in one of the experimental seasons, 2006. The ten DH lines and the two parents differed in the length of the period between GS31 and GS61 by nine days. There was a positive correlation between the duration from GS31 to GS61 and radiation interception during this period which positively affecting grains m '2 Rate and duration of grain growth and final grain weight were assessed for five grain positions (G1 to G5) for Rialto and Spark under 50% shading and a control treatment. Rialto had heavier grains associated with a longer grain filling duration than Spark. The five grain positions had similar durations of grain filling but differed in final grain weight and rate of grain growth. Grains in the central spikelet (G1, G2 and G3) were sink-limited as they did not respond to de-graining. However, grains in the basal (G4) and apical (G5) spikelets were marginally source-limited since their final weight was increased by de-graining. These results suggest that breeders should consider selecting for extra grains in proximal grain positions in basal spikelets (e. g. G4) rather than in distal grain positions in central spikelets, because these grains in this position were heavier, had faster filling rate and had the ability to respond to extra assimilates later in the season. Harvest biomass was positively correlated with grain yield amongst the DH lines. So traits to improve biomass whilst maintaining harvest index may be important for future breeding progress. It is suggested that breeders might select for an extended duration between GS31 and GS61 and higher RUE (via high SLW) to improve grains M-2 and yield potential in future years. They also should select for higher stem carbohydrate reserves to increase source size alongside grain sink size.
28
Shantz, Kim. "1985 Western Plant Breeders Advanced Wheat Yield Trials, Casa Grande". College of Agriculture, University of Arizona (Tucson, AZ), 1985. http://hdl.handle.net/10150/200531.
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Ottman, M. J. "Effect of Planting Date on Wheat Yield in Yuma, 2013". College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2013. http://hdl.handle.net/10150/312151.
Testo completoAbstract (sommario):
Planting dates are known to affect wheat yields. Previous research has shown that the optimum planting date in Yuma is December 15 to January 15. Wheat is sometimes sown later than this in the Yuma area, and earlier planting dates have not been tested. To test a wide range of planting dates, six varieties(Duraking, Havasu, Joaquin, Kronos, WB-Mead, and Yecora Rojo) were planted at two seeding rates (160 and 240 lbs/A) and six planting dates at the beginning of each month from November through April at the Yuma Valley Agricultural Center. Grain yield averaged 6517 (Nov 4), 6339 (Dec 6), 6096(Jan 4), 5712 (Feb 1), 4962(Mar 1), and 3590(Apr 5). The late-flowering varieties performed relatively better at the earlier planting dates. Seeding rates of 160 and 240 lbs/A had no measureable effect on yield overall.
30
Cossani, Rial César Mariano. "Grain yield and resource use efficiency of bread wheat, barley and durum wheat under Mediterranean environments". Doctoral thesis, Universitat de Lleida, 2010. http://hdl.handle.net/10803/8355.
Testo completoAbstract (sommario):
Under Mediterranean environments water and nitrogen (N) are considered the two factors most strongly limiting crop productivity. Wheat (bread and durum) and barley are the main crops grown in dryland Mediterranean environments. Within the Mediterranean basin, wheat is usually cultivated in rotations with other crops under relatively humid zones while barley is sown as a monoculture in the driest zones. Reasons behind barley monoculture are based on an hypothetical barley yield advantage over wheat under stressed environments. However, information about direct comparison between wheat (bread or durum) and barley is not abundant for the Mediterranean basin (nor for other Mediterranean regions). Neither grain yield nor biomass production, water use, nitrogen use or their use efficiency have been compared for the three species to justify the preference of one of them in monoculture in the more scarce resource availability environments. The main objective of the present thesis was to assess the response of wheat (bread and durum) and barley in terms of productivity to different water and nitrogen availabilities within the Mediterranean conditions of dryland cereal regions of Catalonia. Within the main objective two specific objectives were formulated (i) to provide empirical support to the generalized hypothesis of a better performance of barley than wheat under stress conditions, and (ii) to analyze if N fertilization could be a management tool to increase grain yield under stressful Mediterranean conditions for small grain cereals (in cases in which soil N were low). To fulfil the objectives data taken from a literature revision, and historical and regional data were analysed combined with those from five field experiments that were carried-out using different combinations of water and N availabilities for a typical well-adapted and representative cultivar of bread wheat, durum wheat and barley during 2003/04 to 2006/07 growing seasons in a typical dryland region of Catalonia where barley represent c. 80 % of the total cereal acreage.
Across all the experimental conditions grain yield of the three species varied widely from c. 1 to 10 Mg ha-1. Under the driest and poorest yielding conditions barley presented similar yields to wheat (bread and durum) using the experimental data, but also using the bibliographic, historical and regional data, indicating an unjustified barley monoculture in terms of productivity. Despite similar yield between durum wheat and barley a lower stability in grain weight was observed for the case of durum wheat. Neither water use or N use or their use efficiencies supported the hypothesised advantage of barley over wheat across the driest experimental conditions. Water availability and N fertilization modified grain yield, biomass and resource use efficiency. In the present thesis, it was evidenced with realistic field data for the first time that of the degree of co-limitation between factors (N and water in this case) may affect yields as well as water use efficiency of small grain cereals, which had been previously proposed but using simulation models for wheat production in Australia.
31
Ottman, Michael J., e M. T. Rogers. "Irrigation Pracitices and Solum Barley Test Weight and Yield, 2000". College of Agriculture, University of Arizona (Tucson, AZ), 2000. http://hdl.handle.net/10150/204061.
Testo completoAbstract (sommario):
Solum is a barley bred for reduced water use that tends to have low test weight. An experiment was conducted at the Maricopa Agricultural Center to determine the effect of the number of irrigations and their timing on test weight and grain yield of Solum barley. Applying an irrigation at planting and a second irrigation at jointing resulted in the lowest test weight (44.4 lbs/bu) and nearly the highest grain yield (4315 lbs/acre) recorded in the test. All other irrigation treatments resulted in acceptable test weights above 48 lbs/bu except for irrigating at planting plus tillering, which resulted in 47.0 lb/bu test weight. Irrigating at planting and then delaying the second irrigation until boot or later resulted in acceptable test weight but decreased grain yield by 9% or more compared to applying the second irrigation at jointing. Grain yields similar to that obtained by applying a second irrigation at jointing was obtained by delaying the second irrigation until boot and applying a third irrigation at milk or soft dough. This experiment will be conducted a second year before conclusions are drawn.
32
Ottman, M. J., e M. T. Rogers. "Irrigation Practices and Solum Barley Test Weight and Yield, 2001". College of Agriculture, University of Arizona (Tucson, AZ), 2001. http://hdl.handle.net/10150/205392.
Testo completoAbstract (sommario):
Solum is a barley bred for reduced water use that tends to have low test weight. This is the second year of an experiment conducted at the Maricopa Agricultural Center to determine the effect of the number of irrigations and their timing on test weight and grain yield of Solum barley. A single irrigation resulted in low yield (2043 lbs/acre) and unacceptable test weight (45.2 lbs/acre). Two or three irrigations increased yield and test weight in most cases. Applying a second irrigation at the 1 node, 2-3 node, or boot stages resulted in yield of 2694, 2877, and 2670 lbs/acre and test weight of 48.5, 49.0, and 49.5 lbs/bu, respectively. Applying a second irrigation at boot and a third irrigation between flowering and soft dough resulted in an average yield of 3008 lbs/acre and an average test weight of 50.0 lbs/bu. Delaying the second irrigation of Solum barley until boot reduces the risk of lodging and low test weight, and results in high yields.
33
Makgoba, Setlabane Samuel. "Evaluation of different South African wheat cultivators under irrigation for quality and yield parameters in Limpopo Province, South Africa". Thesis, University of Limpopo (Turfloop Campus), 2013. http://hdl.handle.net/10386/1122.
Testo completoAbstract (sommario):
Thesis (M.Sc. (Agronomy)) --University of Limpopo, 2013In South Africa, wheat ranks first among the winter cereal crops produced and plays an important role in the country’s economy. The study was conducted to evaluate different South African wheat cultivars under irrigation for quality and yield parameters in Limpopo province. A field experiment was conducted during 2011 winter growing season under irrigation at the University of Limpopo experimental farm (Syferkuil). Eight wheat cultivars namely: Olifants, CNR 826, SST 347, Baviaans, Duzi, Steenbrass, SST 356 and Krokodil were laid out in a randomized complete block design with four replications for evaluation of yield and quality. The results showed that the highest grain yield obtained was 2372 kg/ha by CNR 826, and the lowest 311 kg/ha by SST 347. Flour yield, break flour yield, flour protein and mixogram development time and water absorption were not significantly different among cultivars. The highest hectolitre mass was 75.13 kghl-1for CNR 826 and the lowest 72.20 kghl-1 for Olifants. The highest falling number obtained was 187.00 sec for SST 347 and the lowest was 81.50 sec for Steenbrass. Cultivars CNR 826, SST 347, Steenbrass and SST 356 showed a good potential on protein content but Krokodil, Olifants and Baviaans had poor protein contents at 9.63%, 9.73% and 10.24% respectively. These results showed that wheat cultivars evaluated were within the requirements of the grading systems of South Africa as regards hectolitre mass and protein content. All these cultivars did not reach the required grade of 220 seconds in falling numbers with Olifants (97.50 sec), CNR 826 (103.50 sec), SST 347 (187.00 sec), Baviaans (146.75 sec), Krokodil (139.50 sec), Steenbrass (81.50 sec) and Duzi (50.25 sec), but only SST 356 met the requirement for utility grade with164.50 seconds. Olifants, CNR 826, Krokodil and Steenbrass yielded above 1500 kgha-1thus showing good potential under Limpopo conditions. These cultivars could be included in future performance evaluations in Limpopo.
34
Jaenisch, Brent Robert. "Plant population and fungicide economically reduce winter wheat yield gap in Kansas". Thesis, Kansas State University, 2017. http://hdl.handle.net/2097/38207.
Testo completoAbstract (sommario):
Master of ScienceDepartment of Agronomy
Romulo P. Lollato
Winter wheat (Triticum aestivum L.) water limited yield potential in Kansas averages 5.2 Mg ha⁻¹; however, state-level yields rarely surpassed 3.4 Mg ha⁻¹. Our objective was to quantify the contribution of individual management practices to reduce wheat yield gaps (YG) economically. An incomplete factorial treatment structure established in a randomized complete block design with six replications was used to evaluate 14 treatments during two years in Manhattan, Belleville, and Hutchinson Kansas. Sites were combined based on tillage practice, growing region in Kansas, and disease pressure. Thus, Manhattan had low disease pressure, was no-tilled, and in eastern Kansas for 2015-16 and 2016-17 (two site years). Meanwhile, Belleville and Hutchinson had high disease pressure, were conventionally tilled, and in central Kansas for 2015-16 and 2016-17 (four site years). We individually added six treatments to a farmer’s practice control (FP) or removed from a water-limited yield control (Y[subscript]w), which received all treatments. Practices were additional split-nitrogen (N), sulfur (S), chloride (Cl), increased plant population, foliar fungicide, and plant growth regulator (PGR). Percent YG was calculated by block and site-year using the Y[subscript]w as reference for potential yield. Orthogonal contrasts indicated yield under no-till which had low disease pressure increased from the FP by the full Y[subscript]w (+0.37 Mg ha⁻¹), but also by the individual practices split-N (+0.28 Mg ha⁻¹), S (+0.26 Mg ha⁻¹), increased plant population (+0.36 Mg ha⁻¹), and fungicide (+0.18 Mg ha⁻¹). In the conventional till which had high disease pressure, wheat yield was increased by 1.18 Mg ha⁻¹ from the Y[subscript]w and by 1.44 Mg ha⁻¹ from the fungicide. The Y[subscript]w and split-N increased grain protein concentration in no-till and conventional-till on average by 9 g kg-1 and 12 g kg-1, respectively. Across all inputs, orthogonal contrasts indicated that the FP yield gap was 8% in no-till which had low disease pressure. Likewise, the orthogonal contrasts indicated that across individual treatments the YG was reduced by split-N (6%), S (5%), Cl (3%), increased plant population (8%), and fungicide (4%). Meanwhile, orthogonal contrasts indicated that the FP yield gap was 20% across all inputs and across individual inputs reduced to 5% from fungicide under conventional-till which had high disease pressure. Fungicide increased net return (+$106.57 ha⁻¹) under conventional-till which had high disease pressure, and increased plant population under no-till which had low disease pressure (+$36.65 ha⁻¹). While a high-cost input (i.e. fungicide) only economically reduced YG greater than 20%; however, a low-cost input (i.e. increased plant population) economically reduced YG less than 20%.
35
Zhou, Bangwei. "Physiological traits associated with recent advances in yield of Chinese wheat". Doctoral thesis, Universitat de Barcelona, 2015. http://hdl.handle.net/10803/291943.
Testo completoAbstract (sommario):
China represents around 20% of world population and this proportion will remain similar in the coming decades, whereas an improvement in diet will increase the consumption of wheat. Although wheat grain yields have been increasing in the last three decades, the challenges of feeding nearly 1.4 billion people will be significant in the next few decades. To satisfy this demand, it is paramount to study what agronomical and physiological traits may contribute to higher yield potential in wheat. Towards this goal, wheats from Henan Province, which is one of the wheat baskets of China, have been studied in this thesis. The objectives of this study were to identify the combination of agronomical, morphological and physiological traits that have contributed to the substantial improvements in yield potential of recently released Chinese winter wheats and to test phenotypical approaches that may help to speed further breeding advances in Chinese wheats.
The yield potential of modern Chinese genotypes has grown as a result of an increase in harvest index (HI), grain number per unit area, and total above-ground biomass, whereas thousand kernel weight has been less affected. By contrast, most of the high yield genotypes are moderately adapted to stress conditions and highly susceptible to yellow rust strains in high-yielding Mediterranean conditions, indicating that stress adaptation has not been a priority in recent Chinese breeding for yield potential conditions. The stress adapted “ ideotype” consists of taller plants with a higher green aerial biomass, particularly during the reproductive stage, together with a better water status, the capacity to take up water during grain filling and a higher nitrogen use efficiency that is related to a more efficient uptake and utilization of N fertilizer. Moreover, the net photosynthesis (Pn) and stomatal conductance (gs) in flag leaves do not appear to be related to increases in yield potential, while total CO2 fixed by the whole ear appears to have a clear role in the yield increase. Studies of carbon (δ13C) and oxygen (δ18O) isotope composition have suggested that higher water use efficiency is involved in raising yield potential. However, such an increase was not achieved through a decrease in gs. By contrast, the high yield potential genotypes have higher nitrogen use efficiency (NUE), N remobilization capacity and uptake capacity during grain filling. These improvements were achieved by optimizing the ear N source/sink balance, which is mainly the result of N released from Rubisco degradation during grain filling.
Besides detecting the physiological traits contributing to raising yield potential, testing for effective phenotyping tools to assess stress tolerance is important in breeding. This is the case for biotic stresses, such as yellow rust, where the use of low cost phenotyping approaches may help to select rust tolerance in the breeding pipeline. The use of conventional (i.e. red/blue/green, RBG) images provided an affordable approach to detect genotypic tolerance to yellow rust. Some colour characteristics, including hue, green fraction, greener fraction, a, and u have proved to be more efficient than other more conventional phenotyping approaches.China representa alrededor del 20% de la población mundial y esta proporción se mantendrá similar en las próximas décadas y por tanto la mejora en la dieta incrementará el consumo de trigo. Aunque los rendimientos de grano en trigo han ido aumentando en las últimas tres décadas, la alimentación de casi 1400 millones de personas en las próximas décadas supone un reto significativo. Para satisfacer esta demanda, es fundamental estudiar qué rasgos agronómicos y fisiológicos pueden contribuir a un mayor rendimiento potencial en trigo. Para lograr este objetivo, los trigos de la provincia de Henan, una de las regiones productoras de trigo de China, se han estudiado en esta tesis. Los objetivos de este estudio fueron identificar la combinación de rasgos agronómicos, morfológicos y fisiológicos que han contribuido a las mejoras sustanciales en el rendimiento potencial de los trigos de invierno chinos recientemente comercializados y evaluar técnicas de fenotípado que pueden ayudar a acelerar los nuevos avances en la selección de trigos chinos. El rendimiento potencial de los genotipos modernos chinos ha aumentado como resultado de un incremento del índice de cosecha (HI), el número de granos por unidad de superfície, y la biomasa aeria total, mientras que el peso de mil granos ha sido menos afectada. Por el contrario, la mayoría de los genotipos de alto rendimiento están moderadamente adaptados a condiciones de estrés y son altamente sensibles a las cepas de roya amarilla en condiciones Mediterráneas de alto rendimiento, lo que indica que la adaptación al estrés no ha sido una prioridad en la selección recientemente realizada en China en condiciones de rendimiento potencial. El “ideotipo” adaptado al estrés consiste en plantas más altas con una mayor biomasa aérea verde, sobretodo durante la etapa reproductiva, junto con un mejor estado hídrico, la capacidad de absorber agua durante el llenado del grano y una mayor eficiencia en el uso del nitrógeno relacionada con una captación y utilización más eficiente de los fertilizantes nitrogenados. Por otra parte, la fotosíntesis neta (Pn) y la conductancia estomática (gs) en las hojas bandera no parecen estar relacionadas con el aumento del rendimiento potencial, mientras que el CO2 total fijado por toda la espiga parece tener un papel claro en el aumento del rendimiento. Estudios de composición isotópica de carbono (δ13C) y oxígeno (δ18O) han sugerido que el aumento de la eficiencia del uso del agua está implicado en el aumento de rendimiento potencial. Sin embargo, dicho aumento no se logró a través de una disminución de la gs. Por el contrario, los genotipos de alto rendimiento potencial tienen una mayor eficiencia en el uso del nitrógeno (NUE), una mayor capacidad de removilización del N y de absorción de agua durante el llenado del grano. Estas mejoras se lograron mediante la optimización del balance fuente / sumidero de N en la espiga, que es principalmente el resultado de la liberación de N procedente de la degradación de Rubisco durante el llenado del grano.
36
Lau, Hoppa. "Impacts of climate variability and climate change on prairie wheat yield". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/MQ58810.pdf.
Testo completo
37
Rajper, Inayatullah. "The effects of sodicity on the growth and yield of wheat". Thesis, Bangor University, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.297714.
Testo completo
38
Avval, M. Bannayan. "Developing and applying crop simulation models for forecast winter wheat yield". Thesis, University of Nottingham, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.285454.
Testo completo
39
Gonzalez, Navarro Oscar. "Understanding the developmental basis of grain yield potential in bread wheat". Thesis, University of East Anglia, 2017. https://ueaeprints.uea.ac.uk/63110/.
Testo completoAbstract (sommario):
Grain yield potential in wheat is a complex trait controlled by sub-traits like grain number, grain size, and assimilate partitioning. To achieve further understanding of grain yield potential, this thesis combines physiological and genetic dissection of wheat development. In particular, how the length of developmental phases can be optimized in favour of increased partitioning of assimilates to the spike, in order to reduce abortion rates of florets. The physiological section of the thesis (Chapter 2 and 3) comprises the in depth study of the CIMCOG panel (CIMMYT Core Germplasm). In this section the variation in patterns of floret and phenological development was determined, ascertaining how these differences affect the number of fertile florets. The differences in floret development were clear in the intermediate florets (floret primordia 3, 4, and 5 from the rachis). Floret survival was found to be positively related to the length of the period of floret development. Also fruiting efficiency, using the frontier concept, show a positive relationship with the stem elongation period. The genetic section (Chapter 4 and 5) involves the use of quantitative trait locus (QTL) analysis with a segregating population to determine the chromosomal locations affecting key developmental traits. A Buster x Charger doubled haploid population provided a crucial contrast between similar genetic background and differences in length of phenological phases. The results show that a QTL on chromosome 7A has an effect on the time to terminal spikelet phase, i.e. the onset of stem elongation, and QTL affecting time to heading was found on chromosomes 2D and 4A. Furthermore, this population also varies in lodging resistance. A major QTL was found on chromosome 2D affecting height and providing lodging resistance. These studies provide the basis to optimise wheat developmental patterns and, therefore, maximize spike fertility.
40
Mistry, Purbasha. "Impact of Climate Parameters on Spring Wheat Yield in North Dakota". Thesis, North Dakota State University, 2016. https://hdl.handle.net/10365/27827.
Testo completoAbstract (sommario):
The impacts of climate change in agriculture is a growing concern. The agricultural sector plays a significant role in North Dakota's (ND) economy, and spring wheat contributes most to the economy. This study focuses on assessing possible impacts of three climate variables on spring wheat yield in ND by building regression model. The trend of average minimum temperature, average maximum temperature, average precipitation and spring wheat yield was analyzed using Mann-Kendall test for 86 years. The study was conducted by dividing ND into 9 divisions. Increasing trend was noticed for 6 divisions for average minimum temperature and average precipitation during growing season. Northeast and Southeast division showed the strongest increasing trend for average minimum temperature and average precipitation, respectively. Eastcentral division had the most decreasing trend for average maximum temperature. Significant relationship was established between spring wheat yield and climatic parameters. The regression model was tested for forecasting accuracy.
41
Derkx, Adinda Pieterdina. "Improving nitrogen use and yield with stay-green phenotypes in wheat". Thesis, University of Nottingham, 2013. http://eprints.nottingham.ac.uk/13025/.
Testo completoAbstract (sommario):
Wheat grain yield is strongly related to nitrogen (N) fertiliser input, a major cost factor and potential environmental pollutant. Much of the grain N requirement is met by N remobilisation from the canopy. Unfortunately, a consequence is canopy senescence and decreased photosynthetic capacity, reducing carbon available for grain-filling. One approach to achieve both higher N use efficiency and grain yield would be to extend the duration of photosynthesis using delayed leaf senescence “stay-green” phenotypes. Three stay-green and two fast-senescing EMS mutants of wheat (cv. Paragon) were characterised. A fast-senescing line, a stay-green line and the wild-type were grown to characterise the interaction between senescence and N availability. Stay-green line SG3 was able to allocate similar proportions of N to the grain under N-limiting and N-sufficient conditions. The accelerated senescence of line FS2 reduced grain yield and N allocation to the grain. Candidate regulatory genes of leaf senescence genes were characterised by correlating their expression with leaf senescence by screening wheat genotypes with varied senescence characteristics in the field. Among the genes were members of the WRKY and NAC transcription factor families that have been related to senescence. Overexpression of the NAC gene resulted in a stay-green phenotype and increased grain N concentrations, but had no effects on shoot biomass or grain yield. Expression of a WRKY-RNAi construct did not reduce WRKY mRNA levels, but led to accelerated leaf senescence and increases in plant height, the number of fertile tillers and grain yield. These results show that the relationships between senescence, nitrogen remobilisation and grain yield are complex and not easily manipulated. The phenotypes and genes identified could contribute to wheat improvement.
42
Wang, Guangyao (Sam), Mario Gutierrez, Michael J. Ottman e Kelly Thorp. "Durum wheat yield prediction at flowering stage for late N management". College of Agriculture, University of Arizona (Tucson, AZ), 2010. http://hdl.handle.net/10150/203775.
Testo completoAbstract (sommario):
Managing late N application effectively in durum wheat is important to reach desirable protein content. Yield prediction at anathesis is needed to estimate N requirement for the crop and N application rate. In this project, we use canopy reflectance and image processing, measured at anthesis, to estimate yield at harvest. Our results of the growing season 2009-2010 suggested that the canopy reflectance index ‘NWI-4’ and the spike pixel size obtained from image processing at anthesis are potential approaches to predict durum wheat yield at harvest. The final goal of this research is to find a simple and rapid method to manage late N fertilizer to reach desirable grain protein content.
43
Saieed, Md Atik Us. "Identification and characterization of novel genes contributing to wheat grain yield". Thesis, Saieed, Md Atik Us (2022) Identification and characterization of novel genes contributing to wheat grain yield. PhD thesis, Murdoch University, 2022. https://researchrepository.murdoch.edu.au/id/eprint/66631/.
Testo completoAbstract (sommario):
Grain yield is one of the most important aspects of wheat breeding. Being a polygenic trait, wheat grain yield is regulated by multiple genes and influenced by environmental factors. It is a complex trait which is linked to several traits such as seed number, thousand kernels’ weight etc. The interaction of these yield components with environmental stimulus are poorly understood. In the current study, to improve our understanding, phenotypic plasticity of contributing traits to the grain yield was explored. The phenotypic plasticity is the variations in the expressed phenotype by an individual genotype under environmental influences. The experiment consisted of 225 Westonia-Kauz double haploid (DH) lines and evaluated in five environmental conditions. The result demonstrated that, across the DH lines, the spikelets/spike was the most plastic trait. The least plastic character was the grain protein content. Yield plasticity was found higher at favourable conditions. An increase in yield plasticity by 0.1 units was associated with an increase in maximum yield by 4.45 kg ha−1 (p≤0.001). The generated knowledge regarding trait plasticity will be useful in dissecting the genetics for yield improvement particularly at the situation of rapid climate change. Identifying quantitative trait loci (QTL) and incorporating them in the breeding program has been a widely used approach for genetic improvement of yield and its components. QTL mapping suggests a considerable size of chromosomal location harbouring genes contributing to the trait which also contains many non-target genes. Thus, a more precise identification of contributing gene would be much helpful for an efficient breeding approach. However, functional confirmation of each individual gene of a QTL region is quite laborious and expensive work. In-silico approach provides the opportunity to reduce the down-stream workload by reducing the number of candidate genes in a systematic approach. Apart from the trait plasticity research, the current study also used a pipeline combining bioinformatics and laboratory approaches to identify the contributing genes of a grain yield QTL from a double haploid (DH) population of Westonia × Kauz. Assembling the QTL region on the International Wheat Genome Sequence Consortium (IWGSC) whole-genome sequence using the flanking 90K SNP markers identified the genomic region of 20 Mbp. Gene annotation revealed 16 high confidence genes and 41 low confidence genes in that genomic region. Further functional gene annotation, ontology investigation, pathway exploration, and gene network study using publicly available expressional data enabled short-listing of four genes for down-stream functional confirmation. Complete sequencing of those four genes demonstrated that only two genes namely ferredoxin-like protein and tetratricopetide-repeat (TPR) protein gene are polymorphic between the parental cultivars. Two single nucleotide polymorphism (SNP) variations were observed in the exon for both genes, and one SNP resulted in changes in amino acid sequence. The qPCR-based gene expression showed that both genes were highly expressed in the high-yielding double haploid lines. In contrast, gene expression was significantly lower in low-yielding lines. Results indicate that these two genes are potentially the underlying genes for the grain yield QTL. To investigate the association of the selected genes with grain yield and yield components at a wider level, further genetic and phenotyping experiments were conducted on a set of 143 historical wheat cultivars of Australia. For both genes, the identified alleles in the parental cultivars have been named as Westonia and Kauz allele. Characterising the allelic composition of the genes demonstrated that, for ferredoxin gene, 34.9% cultivars possessed Westonia allele and 16.9% cultivars possessed Kauz allele. In case of TPR gene, 20.9% cultivars possessed Westonia allele and 23.8% cultivars possessed Kauz allele. For both genes, cultivars having Westonia allele showed significantly higher seed width, thousand kernels’ weight and grain yield at different environmental conditions which clearly indicated that these genes are playing important roles in determining grain yield. For further level of functional confirmation, CRISPR-Cas9 based genome editing experiment was carried out on the TPR gene in Arabidopsis using orthologous gene. Agrobacterium mediated floral dip transformation was performed using immature inflorescence containing Cas9 gene. Knock-out mutants were selected by sequencing the target gene. Phenotypic data were collected from T2 generation on leaf length, stem length, number of branches on the main stem, days to flowering, days to maturity, pods/plant, and pod length. A significant reduction was observed in pods/plant, leaf length, and days to flowering and maturity. Gene expression analyses was performed on the selected genes responsible for increased seed size, seed number, and vegetative growth, in transgenic lines of Arabidopsis. Significant reduction in gene expression was observed for ARGOS, GRF1 and GW2 genes suggesting the role of TPR gene in downregulating essential growth regulator genes and its involvement in grain yield indirectly. Overall, this study demonstrated successful use of multiple research approaches in identification of a novel candidate genes of a yield related QTL. This approach can be utilised in exploring the candidate genes of other QTLs. The identified novel genes demonstrated the potential of improving the wheat grain yield which might be included in the breeding program for further yield improvement.
44
Knowles, Tim C., Michael J. Ottman e Rock Cramer. "Influence of Nitrogen Fertilizer Applied at Flowering on Durum Wheat Grain Yield and Quality". College of Agriculture, University of Arizona (Tucson, AZ), 1996. http://hdl.handle.net/10150/202440.
Testo completoAbstract (sommario):
Application of nitrogen (N) fertilizer in conjunction with the irrigation event occurring closest to the flowering stage is effective in reducing the incidence of yellowberry and boosting grain protein levels of durum wheat. However, N applications at this time normally do not increase grain yield, except perhaps on very sandy soils. A field experiment was conducted to determine the profitability of applying 35 pounds of N per acre at flowering to durum wheat to avoid dockage for poor grain quality. Two treatments consisted of a check plot with no N applied at flowering and UAN 32 water run at a rate of 35 lbs. N /acre to basin irrigated durum wheat grown on a loamy sand soil. Maximum durum wheat grain yield (6157 lbs. /acre), protein concentration (13.7 %), and corrected income per acre ($480.31) was obtained with the N fertilizer application. In fact, N fertilization at flowering on this sandy soil increased durum wheat grain yield by 255 lbs. /acre compared to the unfertilized plot.
45
Ottman, Michael J. "Wheat and barley varieties for Arizona, 2015". College of Agriculture, University of Arizona (Tucson, AZ), 2015. http://hdl.handle.net/10150/581481.
Testo completo
46
Mashaba, Zinhle. "Modelling dryland winter wheat yield using remotely sensed imagery and agrometeorological parameters". Diss., University of Pretoria, 2017. http://hdl.handle.net/2263/60634.
Testo completoAbstract (sommario):
Wheat consumption has become more widespread and is increasing in South Africa especially in the urban areas. The wheat industry contributes four billion rands to the gross value of agriculture and is a source of employment to approximately 28 000 people. Wheat yield forecasting is crucial in planning for imports and exports depending on the expected yields and wheat health monitoring is important in minimizing crop losses. However, current crop surveying techniques used in South Africa rely on manual field surveys and aerial surveys, which are costly and not timely (after harvest). This research focuses on wheat health monitoring and wheat yield prediction using remote sensing, which is a cost effective, reliable and time saving alternative to manual surveys. Hence, the research objectives were: (i) to identify remotely sensed spectral indices that comprehensively describe wheat health status. (ii) Develop an Normalized Difference Vegetation Index (NDVI) based wheat yield forecasting model and (iii) to evaluate the impact of selected agrometeorological parameters on the NDVI based forecasting model. Landsat 8 images were used for determining spectral indices suitable for wheat health monitoring by relating the spectral indices to the land surface temperature. Results show that the Normalized Difference Water Index (R2 between 0.65 and 0.89) and NDVI (R2 between 0.36 and 0.62) were the most suitable indices for wheat health status monitoring. Whereas, the Normalized Difference Moisture Index (R2 between 0.53 and 0.79) and the Green Normalized Difference Vegetation Index (R2 between 0.28 and 0.41) were found to be less suitable for wheat health monitoring. Moderate Resolution Spectroradiometer (MODIS) derived NDVI for fourteen years was used to build and test a wheat yield forecasting model. The model was significant with an R2 value of 0.73, a p-value of 0.00161 and an RMSE of 0.41 tons ha-1. The study established that the period 30 days before harvest during the anthesis growth stage, is the best period to use the linear regression model for wheat yield forecasting. Satellite derived agrometeorological parameters such as: soil moisture, evapotranspiration and land surface temperature were added to the NDVI based model to form a multi-linear regression model. The addition of these parameters to the NDVI model improved it from an R2 of 0.73 to an R2 of 0.82. Through the use of a correlation matrix, the NDVI (r=0.88) and evapotranspiration (r=0.58) were highly correlated to wheat yield as compared to soil moisture (r=0.27) and land surface temperature (r=-0.02). This research provided evidence that remote sensing can be used at acceptable levels of accuracy for wheat monitoring and wheat yield predictions compared to manual field surveys which are costly and time consuming.Dissertation (MSc)--University of Pretoria, 2017.
Agricultural Research Council
National Research Foundation
Spatial Business IQ
GeoTerra Images
University of Pretoria
Geography, Geoinformatics and Meteorology
MSc
Unrestricted
47
Balasubramaniam, Rengasamy. "The effects of foliar diseases and irrigation on root development, yield and yield components of wheat (Triticum aestivum L.)". Lincoln College, University of Canterbury, 1985. http://hdl.handle.net/10182/1514.
Testo completoAbstract (sommario):
Studies were conducted on three field trials of wheat cv. Kopara to investigate the lack of compensation by later determined components of yield because of early disease constraints. The investigation was based on the hypothesis that early disease reduces root development and thus causes the plants to be water constrained at later growth stages when soil water deficits usually occur. The reduced root development and soil water deficits may reduce the ability of the plant to compensate for reductions in early determined components. The hypothesis was tested by the application of irrigation to alleviate water stress. In a disease free crop, the possible phytotonic effects of the fungicides benomyl and triadimefon on wheat were investigated. These fungicides had no phytotonic effects on shoot, root growth, or yield under the prevailing conditions. The effect of disease on root development was analysed by root length measurements. Disease present in the crop at any stage of growth affected root development. Root development in the upper zones of the soil profile was reduced more by disease compared to those zones below 35 cm. A full disease epidemic reduced root development more than an early or late disease epidemic. The early and late disease epidemics had similar effects on root length. Alleviation of early disease constraints enabled greater development of roots to offset any earlier reductions. Soil water deficits increased root development in the lower zones of the nil disease plants. The presence of adequate soil water from irrigation reduced the requirement for further root growth in all treatments. In the 1981-1982 field trial a full disease epidemic reduced yield by 14% whereas an early disease epidemic reduced yield by 7%. The reduction in yield was attributed to a lower grain number. With irrigation the yield reduction in the full disease plants was 12% whereas in the early disease plants the reduction was only 2.4%. This indicated that plants affected by the early disease epidemic were water constrained. In this study, the results suggested that, for conditions prevailing in Canterbury, the supply of water at later growth stages increased grain weight in plants which were subject to early disease epidemics. This suggests that reduced root development caused by early disease and soil water deficits may prevent compensation by grain weight. Water use was similar in all disease treatments. After irrigation the irrigated plants of all treatments used more water. Disease affected water use in relation to yield production however, and was better expressed by water use efficiency. Water use efficiency was reduced in the full disease plants. A stepwise regression analysis suggested that water use efficiency was affected directly by disease at later growth stages, and indirectly via an effect on total green leaf area at early growth stages. This study partially proves the hypothesis that reductions in root development caused by an early disease epidemic may constrain the plants at later growth stages when water deficits usually occur. It was shown that the reduction in root development caused by disease could be counteracted by irrigation. In this respect, water served as a tool to study the effect of disease constraints on the yield of wheat. A knowledge of cereal crop physiology, root growth and function is used to explain and discuss the observations made in this research programme. The results are discussed in relation to the way in which disease affects yield through its effect on root development. The possible reasons for the continued effects of disease even after the control of disease at later growth stages are discussed. The economic use of fungicides and water in diseased crops are also outlined. Suggestions for future studies on disease-yield loss relationships are provided. The repetition of these experiments in different sites and climatic regions could provide information which may be incorporated in disease-yield loss simulation models. This could then be used to predict root development and water requirements of diseased plants, and provide a basis for economic use of fungicides and water, and for better disease management programmes.
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Kindred, Daniel R. "Investigating heterosis for yield, breadmaking quality and nitrogen use efficiency in wheat". Thesis, University of Reading, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.412168.
Testo completo
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Bullard, Amanda Simpson. "Protein Indicators, Quality, and Yield of Winter Durum Wheat Grown in Virginia". Thesis, Virginia Tech, 1999. http://hdl.handle.net/10919/35457.
Testo completoAbstract (sommario):
Durum wheat (Triticum durum Desf.) is produced primarily in the Northern Great Plains and the Pacific Southwest of the United States. Current germplasm is predominantly of the spring growth habit. The objective of this study was to determine the feasibility of winter durum production in Virginia based upon both yield and quality parameters. Adaptation and yield potential of available winter durum lines were assessed from 1993-1998, in three physiographic regions in Virginia. The highest average durum yields were produced in the northern piedmont plateau at the Orange County location. Winter durum yields generally averaged 1600-2800 kg/ha less than soft red winter wheat, traditionally grown in the state. The price premium for high quality durum can compensate for this difference in yield. Based on average durum yields, and assuming the grain meets U.S. No. 2 Hard Amber Durum standards, durum production in Virginia would have been more profitable than soft red winter wheat production in 1994 and 1997. Physical and chemical quality analyses of the top 19 performing durum lines were performed to determine grain marketability, suitability for pasta, and potential consumer acceptance of the end product. Protein content and gluten strength of the Virginia grown durum were acceptable. Color, firmness, and cooking loss of pasta produced from Virginia grown durum were comparable to pasta produced from commercial semolina. Requirements for U.S. No. 2 Amber Durum were met by 21% of the lines in both 1996 and 1997. Overall, the wet, humid Virginia climate was the greatest hindrance to durum production and quality. The field trials and quality analyses showed that high quality durum production in Virginia is possible, but not consistent over all years.Master of Science
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Wagner, Nicole Catherine. "Wheat yield prediction modeling for localized optimization of fertilizer and herbicide application". Diss., Montana State University, 2004. http://etd.lib.montana.edu/etd/2004/wagner/WagnerN0805.pdf.
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