Tesi sul tema "Wheat Physiology"

A series of experiments were carried out in solution culture in growt~ ~ooms and a glasshouse, to study the effects of sallnlty on leaf extension rate ion concentrations, sap osmotic pressure, net photosynthesis and related parameters, stom~tal frequency, specific leaf weight and a number of agronomlc parameters of spring wheat. Rate of net photosynthesis, transpiration rate, stomatal conductance and sub-stomatal carbon dioxide concentration per unit area of leaf were determined using an Infra-red Gas Analyser. Experiments 1 and 3 were conducted in growth rooms set at a temperature cycle of 24°Cj16°C day and night and photoperiod of 16 hours. The seedlings received light from a bank of 125W fluorescent 'warm white' lights which provided between 200-300 ~mol m- 2 s-l photosynthetically active radiation at initial plant level. Experiments 2, 4 and 5 were carried out in a glasshouse with no control of light and temperature. In Experiment 1 the salinity treatments tested were control (0 mol m- 3 NaCI), 'constant' and 'variable' salinity. In the constant salinity treatment plants were grown at 100 mol m- 3 NaCI all the time after initial salt stress. In the variable salinity treatment a 12 day cycle was repeated with daily increments of 10 mol m- 3 NaCI after initial salt stress of 50 mol m- 3 NaCI till it reached to 150 mol m- 3 NaCI. During the final two days of the cycle salinity was stepped down from 150 to 100 to 50 mol m- 3 NaCl. In Experiment 2 the salinity levels tested were 0, 50, 100 and 150 mol m- 3 NaCI. CaCI was added in this and later experiments at 20:1 (mol Na~:mol ca2+) ratio. The results of the both Experiments 1 and 2 suggested that salinity had no effect on leaf appearance stage but tiller production was decreased. Salinity decreased leaf extension rate and final leaf length but leaf extension duration was not affected. Although leaf extension rate was the main factor influencing final leaf length, there were no consistent quantitative relationships between these parameters in different leaves and at different salinity levels. Plants in variable salinity performed better than those in constant salinity but these treatments were not significantly different and gave similar results. The results of Experiment 2 showed that a gradient of Na+ and Cl- concentrations was found in different leaves. Higher Na+ and Cl- concentrations were found in lower leaves than in expanding leaves. Calculated Na+ and CI- contents (ion concentrations x dry weight) suggested that these ions were mainly located in roots, stem and tillers irrespective of salinity levels. The effect of salinity was to increase concentrations of leaf Na+, Cl- and sap osmotic pressure in the youngest fully expanded leaves whereas K+ concentration was inconsistently affected. When gas exchange measurements were made in situ on leaves, light intensity showed wide i variation due to movement of clouds. Variations in light intensity and absence of any equilibration prior to measurements made it difficult to detect any effects of salinity on gas exchange. Therefore to determine the effects of salinity on gas exchange in expanding and senescing leaves, in Experiments 3, 4 and 5, a strong light source capable of providing photon flux densities at or near light saturation for gas exchange was used. In Experiments 3 and 4 light response curves were produced using neutral density filters. Using an exponential model, maximum net photosynthesis photosynthetic efficiency, photon flux compensation point and dark respiration for salinities and leaf insertions were calculated. In Exper~~ent 3 the .s~linity levels tested were 0, 100 and 200 mol m NaCI. Sa11n1ty decreased green lamina area, maximum and net photosynthesis, stomatal conductance, transpiration rate, leaf productivity but increased dark respiration and photon flux compensation point. Photosynthetic efficiency and transpiration efficiency were inconsistently affected. In Experiment 3 at 200 mol m- 3 NaCI leaf 6 senesced rapidly. Therefore in Experiment 4 the salinity levels tested were 0, 75 and 150 mol m- 3 NaCI. In Experiment 4 the parameters studied were identical to those in Experiment 3 except that the measurements were performed on leaf 5 and the flag leaf. In Experiment 4 a similar trend for gas exchange parameters was noted at 0 and 150 mol m- 3 NaCl but at 75 mol m- 3 NaCI Pn was higher than in the control due to delayed senescence. In both Experiments 3 and 4 leaf sap Na+, CI- and osmotic pressure increased and Pn decreased during senescence but there were no consistent relationships between these parameters for different leaves and salinity treatments. Experiments 2, 3 and 4 suggested that salinity increased stomatal frequency per unit leaf area but stomatal frequency per leaf and specific leaf weight were inconsistently affected. Experiment 5 was conducted to examine the effects of salinity on changes in gas exchange in the flag leaf and two penultimate leaves simultaneously. The salinity levels tested were 0, 75 and 150 mol m- 3 NaCI. The leaf x salinity interaction showed that salinity had larger effects on the flag leaf than leaves 2 and 3. The leaf x salinity interaction was significant for leaf temperature, net photosynthesis, stomatal conductance, transpiration rate and transpiration efficiency but not for sUb-stomatal carbon dioxide concentration. Salinity significantly decreased all the yield components and grain yield. The results of these experiments suggest that salinity had large effects on photosynthesis, dry matter production and grain yield and that ion concentrations do not determine the observed changes in net photosynthesis with leaf age in salt stressed plants.

The greening of etiolated first leaf blades of wheat (Triticium aestivum Mercia) seedlings (referred to in the text as leaf tissue) was studied in relation to tissue age and water stress. Use was made of whole seedlings, excised leaf blades and leaf blade segments. Responses to photoperiodic illumination were measured as changes in the levels of chlorophyll, total soluble protein and nucleic acids (both total and specific fractions). The pattern of greening in the whole seedlings, excised leaf blades and leaf blade segments was essentially the same in 6 and 10 day-old dark-grown tissues, where chlorophyll accumulation followed the age sequence along the leaf. Least chlorophyll accumulated in the tip of leaves of both ages but the older leaves contained less overall pigment than the younger leaves. Patterns of total soluble protein and total nucleic acid accumulation did not reflect the pattern shown by the chlorophyll. Protein accumulated most in the tip region, with nucleic acids being highest in the middle region. Water stress treatment reduced chlorophyll accumulation in leaf blade tissue, particularly in the intact seedlings. Protein levels, however, were more variable and appeared to reflect the ability of the younger tissue to accumulate this compound as a stress metabolite. Total nucleic acid levels were also elevated under water stress. Again, these effects were most marked on the intact seedlings, implying that an effect on the roots was also involved. The data from polyacrylamide gel electrophoresis of RNA fractions showed that the level of chloroplast RNA components was maintained up to 17 days for tissue incubated in the dark as well as in the light. Severe water stress treatments applied to the roots of whole seedlings resulted in the loss of ribosomal fraction in the leaves. However, this effect was not seen with mild water stress. Kinetin treatments during water stress did not appear to alter the pattern of cell component accumulation although in unstressed material, treatment with this compound enhanced chlorophyll accumulation slightly, especially in the young tissue. This indicates that, at the concentration used, the growth regulator was not able to alleviate the stress condition. The leaf blades of intact seedlings responded in a specific way which was much more pronounced than for excised leaf blades or leaf blade segments. It was concluded that some signalling was involved between the root and shoot tissues during water stress treatments.

Germinating uredospores of race C17 of Puccinia graminis f.sp. tritici form characteristic infection structures (appressorium, infection peg, vesicle, infection hypha) in response to a 1.5 h heat shock at 29° C administered 2 h after germination at 19° C. The proportion of sporelings forming infection structures was augmented by nutrients, n-nonyl alcohol and, an appropriately timed heat shock. The heat shock temperature required to induce maximum differentiation had a very precise optimum which varied slightly for each spore lot. Variations one degree above or below this optimum reduced the percent differentiation by greater than 40%. The presence of an inhibitor of protein synthesis, puromycin, in the germination medium: (1) prevented uredosporeling differentiation but had no effect on germination, (2) significantly reduced the proportion of germtubes forming appressoria, and (3) in most cases prevented the division of germtube nuclei. It was concluded that essential differentiation-specific proteins are synthesized from the onset of germination, throughout the formation of appressoria and to the completion of differentiation. These results were consistent with the observed effects of heat shock on the rate of protein hydrolysis. During germination there was a net hydrolysis of protein leading to an increase in size of the endogenous pool of free amino acids and to an increased leakage of amino acids to the germination medium. Heat shock effectively reduced the amount of endogenous free amino acids and the extent to which amino acids were lost to the medium. It was concluded that in heat shocked sporelings protein synthesis was increased relative to protein hydrolysis by comparison with the relative rates of these two processes in germinating (non-shocked) uredosporelings. Moreover, there was no net protein synthesis during the formation of infection structures induced by heat shock. The loss of amino acids to the germination medium was selective, particularly in heat shocked sporelings.
Land and Food Systems, Faculty of
Graduate

The plant hormone gibberellin (GA) is known to influence grain size and flour quality, flowering, development and germination in wheat. GA also induces the production of α-amylase by the aleurone layer and premature production of this enzyme during development results in degraded starch in the mature grain. While GA is proposed to have a negative effect on flour quality, it is essential for early grain development and these effects are separated both temporarily and spatially in the grain. It was the aim of this project to further understand the role GA plays in wheat grain development and in order to achieve this constructs were designed to alter GA metabolism or signalling in the seed-coat, endosperm, embryo or aleurone of developing wheat grains. In plants where GA content was manipulated in the developing endosperm it was shown that GA produced by this tissue is involved in regulating grain size and morphology. This was demonstrated by the differences observed between the transgenics and their nulls in grain size, hardness index and moisture content. Additionally, in these lines no differences were observed in the α-amylase levels, implying that GA produced by the endosperm might not be influencing the production of this enzyme. However, GA insensitivity introduced in the embryo and aleurone layers did not display the hypothesised phenotypes and was inconclusive in determining the role of GA signalling in grain development. During this project a reliable qPCR based method using TaqMan assays was also developed to determine zygosity of transgenic plants in the T1 generation. This method was successful in reducing the number of generations required to select homozygous material compared to more conventional methods.

[Truncated abstract] Lophopyrum elongatum, a wild relative of wheat, can be used as a source of novel genes for improving the salt tolerance of bread wheat. Na+ `exclusion? is a major physiological mechanism for salt tolerance in the wheat L. elongatum amphiploid, and a large proportion (~50%) of the improved Na+ `exclusion? is contributed by a gene(s) on chromosome 3E. This study integrated physiological analysis with comparative genomics to identify gene orthologues that may regulate Na+ transport, and designed and implemented molecular markers for developing wheat L. elongatum recombinant lines with reduced portions of L. elongatum chromatin retaining the Na+ `exclusion? trait. Physiological analysis of leaf Na+ accumulation in wheat L. elongatum substitution lines confirmed that the 3E chromosome contributes a major effect on reduced leaf Na+ accumulation in wheat when grown at 200 mM NaCl. Candidate genes from the model plant, Arabidopsis thaliana, controlling Na+ transport into and from cells (SOS1, HKT1) or compartmentalisation within vacuoles (NHX1, NHX5, AVP1, AVP2) were targeted for comparative analysis in wheat. Wheat gene orthologues were identified by BLAST searching to identify either FL-cDNAs or ESTs, which were subsequently used to amplify genomic DNA, and orthologues confirmed by similar intron-exon structure between Arabidopsis and rice. Intron-exon comparisons showed the majority of exons were conserved between Arabidopsis, rice and wheat, but also indicated exon shuffling events since divergence from a common ancestor. Gene orthologues were assigned to homoeologous chromosomes and non-syntenic regions between wheat and L. elongatum, with the SOS1 orthologue located on group 3 chromosomes in wheat and L. elongatum. ... The recombinant line 524-568 contains a small introgression on the distal end of the long arm of wheat chromosome 3A and represents the most desirable line presently available for further germplasm development. The main outcomes of this thesis have been an increased understanding of the physiology and evolution of orthologues for Na+ transport in wheat and L. elongatum, improved methodologies for designing alien-specific PCR markers, and the development of overlapping recombinant lines that provide a source of novel genes for pyramiding into wheat and improving its tolerance to salt stress.

Master of Science
Department of Agronomy
Krishna Jagadish
Post-flowering heat stress is one of the major environmental constraints for wheat (Triticum aestivum L.) production in the state of Kansas, where wheat is the most widely grown grain crop. Studies have shown that the optimal temperature for wheat grain development is approximately 21°C. During the grain filling stage for wheat in Kansas, it is fairly common for temperatures to reach more than 30°C and above. These scenarios have resulted in lower productivity and yield in Kansas compared to other regions of the United States. Therefore the objectives of this research project included: phenotyping seven Kansas varieties for post-flowering heat tolerance in a controlled environment growth chamber study as well as in two field experiments, estimation of spike and flag leaf senescence in wheat exposed to post-flowering heat stress, and identifying potential genetic donors for heat tolerance from winter wheat breeding lines and Near Isogenic Lines developed from Kansas State University’s Wheat Breeding Program. To impose heat stress in the controlled growth chambers, plants grown at 25°C were transferred to high day temperature (35°C) chambers ten days after the first sign of anthesis. Under field conditions, custom built “heat tents” were placed over the wheat plots ten days after first flowering and remained until maturity. Plants grown under heat stress exhibited early senescence, indicating a shorter grain filling period compared to the controls. Early-maturing varieties recorded greater percent reductions in grain yield under heat stress. Post-flowering heat stress induced significant reductions in thousand kernel weight, grain number, harvest index, and grain yield. Spike and flag leaves effective quantum yield of PSII was reduced more drastically under growth chamber stress exposure compared to field grown plants. Significant genetic variation in the spike and flag leaf senescence initiation and the differential rate of senescence among the seven tested varieties suggested the potential for considering this trait in breeding programs. Compared to the commercially relevant varieties, breeding lines varied less under heat stress with a few lines recording a greater degree of heat resilience and experienced little to no drop off in heat stress conditions compared to control. The reduced performance under heat stress for the seven varieties highlights the genuine need to explore wider genetic diversity, including wild wheat, to infuse greater resilience into ongoing wheat breeding programs. However, the results observed in the breeding lines indicate that introducing larger genetic diversity may aid in developing greater heat stress resilient wheat varieties for current and future changing climate.

Doctor of Philosophy
Department of Agronomy
P. V. Vara Prasad
Drought and high temperature are major detriments to global wheat production. Wheat varies in its susceptibility to drought and high temperature stress. Three experiments were performed to address the challenges of drought and high temperature stress in wheat. The first experiment consisted of 256 genotypes of spring wheat and 301 genotypes of winter wheat, field screened for yield traits related to drought tolerance, in irrigated and dryland experiments. The experimental designs for the first experiment were both augmented incomplete block designs with one-way or row-column blocking. This experiment was performed at the Ashland Bottom Research Farm, south of Manhattan, KS, between 2011-2013. From this experiment, three conclusions were made: wheat genotypes vary widely in their responses between dryland and irrigated treatments and this variation can be used in future experiments or breeding tolerant genotypes. The number of seeds per unit of area, total biomass per unit area, and the average weight of one thousand seeds, were the best yield traits for predicting yield in both irrigated and dryland environments. Twenty genotypes were selected for future research based on their susceptibility or tolerance to drought. The second experiment was performed in the greenhouse facilities to observe the source-sink relationship of spring wheat genotype Seri 82 under drought and defoliation. The experiment was a randomized complete block design with a split-plot treatment arrangement. Post-anthesis cessation of watering and defoliation were the treatments. Both water stress and defoliation affected seed yield and total biomass. The major effect of post-anthesis water stress was a decrease in single seed weight. Defoliation affected the source-sink relationship by reducing the source strength of the leaves. This caused the stem to contribute more to overall yield. The defoliation also caused the remaining leaves to compensate for the removed leaves. The final experiment evaluated the changes in seed-filling rate and duration of three winter wheat genotypes during high temperature stress. High temperature stress reduced the duration of seed fill and increased the rate, differently in each genotype. Higher yields in the winter wheat growing regions, susceptible to post-anthesis high temperature stress, may be possible through selection of cultivars with faster seed-filling rates and/or duration of seed filling.

High temperature (HT) stress during wheat male reproductive development causes irreversible damage to the anther tapetum layer and the developing microspores it supports, resulting in reduced yield. With the frequency of pre-flowing temperature stress events likely to increase, a better understanding of the effects of high temperature stress on anther developmental regulation is required. Gibberellin (GA) signalling has been shown to regulate tapetum programmed cell death (PCD) and pollen coat formation via the transcription factor (TF) GAMYB. This project aimed to investigate the function of two putative GA-signalling components in wheat anther development and characterise the global hormonal and transcriptional anther responses to HT. RNAi and TILLInG mutants for TaGAMYB and a putative orthologue of a rice tapetum PCD component, TabHLH141, revealed that both are required for male fertility. Tagamyb mutants displayed stunted anther development with irregular tapetum vacuolisation and reduced pollen viability. An interaction between RHT-D1 and TabHLH141 suggests that GA may mediate anther development through regulation of DELLA-TF interactions. Having characterised and developed a non-destructive staging method for wheat anther development, RNA-Seq and global hormone analysis was used to investigate the response to HT stress around pollen mother cell meiosis. Significant changes in expression of tapetum metabolism and PCD annotated transcripts and anther GA, auxin and jasmonate concentrations indicates that hormonal regulation of HT-responsive transcription may contribute to defective anther development. The work in this project demonstrates that advanced functional genomics techniques can be now be applied to the dissection of complex signalling pathways in hexaploid wheat.

In the developing endosperm of bread wheat (Triticum aestivum), seed storage proteins are produced on the rough endoplasmic reticulum (ER) and transported to protein bodies, specialised vacuoles for the storage of protein. The important gluten proteins of wheat are transported to the protein bodies they are stored in by two distinct routes. One route consists of vesicles that bud directly off the ER, while the other involves transport through the Golgi (Arcalis et al, 2004). In plants, the RabD clade mediates ER to Golgi vesicle transport (Batoko et al, 2000). Available sequence information for Rab GTPases in Arabidopsis, rice, Brachypodium and bread wheat was compiled and compared in phenetic trees. Partial genetic sequences were assembled using the first draft of the Chinese Spring wheat genome. A suitable candidate gene from the RabD clade (TaRabD2a) was chosen for down-regulation by RNA interference (RNAi) and an RNAi construct was used to transform wheat plants. Using real time PCR, all four available RabD genes were shown to be knocked down in the developing endosperm of transgenic wheat. The transgenic grain was found to produce flour with significantly altered processing properties when measured by farinograph and extensograph. SE-HPLC found that a smaller proportion of HMW-GS and large LMW-GS are incorporated into the glutenin macropolymer in the transgenic dough. Lower protein content but a similar protein profile on SDS-PAGE was seen in the transgenic grain

Doctor of Philosophy
Department of Agronomy
P.V. Vara Prasad
High temperature (HT) and drought are detrimental to crop productivity, but there is limited variability for these traits among wheat ([italics]Triticum aestivum[end italics] L.) cultivars. Five [italics]Aegilops[end italics] species were screened to identify HT (52 accessions) and drought (31 accessions) tolerant species/accessions and ascertaining traits associated with tolerance. Four synthetic wheats were studied to quantify independent and combined effects of HT and drought. [italics]Aegilops[end italics] species were grown at 25/19°C day/night and 18 h photoperiod. At anthesis, HT was imposed by transferring plants to growth chambers set at 36/30°C, whereas in another experiment, drought was imposed by withholding irrigation. Synthetic wheats were grown at 21/15°C day/night and 18 h photoperiod. At anthesis or 21 d after anthesis, plants were exposed to optimum condition (irrigation + 21/15°C), HT (irrigation + 36/30°C), drought (withhold irrigation + 21/15°C), and combined stress (withhold irrigation + 36/30°C). Stresses were imposed for 16 d. High temperature and drought stress significantly decreased chlorophyll, grain number, individual grain weight, and grain yield of [italics]Aegilops[end italics] species (≥ 25%). Based on a decrease in grain yield, [italics]A. speltoides[end italics] and [italics]A. geniculata[end italics] were most tolerant (~ 61% decline), and [italics]A. longissima[end italics] was highly susceptible to HT stress (84% decline). Similarly, [italics]A. geniculata[end italics] had greater tolerance to drought (48% decline) as compared to other species (≥ 73% decline). Tolerance was associated with higher grains spike [superscript]-1 and/or heavier grains. Within [italics]A. speltoides[end italics], accession TA 2348 was most tolerant to HT with 13.5% yield decline and a heat susceptibility index (HSI) 0.23. Among [italics]A. geniculata[end italics], TA 2899 and TA 1819 were moderately tolerant to HT with an HSI 0.80. TA 10437 of [italics]A. geniculata[end italics] was the most drought tolerant accession with 7% yield decline and drought susceptibility index 0.14. Irrespective of the time of stress, HT, drought, and combined stress decreased both individual grain weight and grain yield of synthetic wheats by ≥ 37%, 26%, and 50%, respectively. These studies suggest a presence of genetic variability among [italics]Aegilops[end italics] species that can be utilized in breeding wheat for HT and drought tolerance at anthesis; and combined stress of drought and high temperature on synthetic wheats are hypo-additive in nature.

Development of winter wheat (Triticum aestivum L.) cultivars capable of more efficient uptake and utilization of applied nitrogen (N) has the potential to increase grower profitability and reduce negative environmental consequences associated with N lost from the plant-soil system. The first study sought to evaluate genotypic variation for N use efficiency (NUE) and identify lines consistently expressing high or low NUE under two or more N rates in a total of 51 N-environments. The results indicated that significant genotype by N rate interactions were frequently observed when trials utilized at least three N rates and identified wheat lines with high and stable yield potential that varied in performance under low N conditions. In addition, NUE was associated with above-ground biomass at physiological maturity were found to be both highly heritable across multiple N supplies. In the second study, two bi-parental mapping populations having a common low ('Yorktown') and two high (VA05W-151 and VA09W-52) NUE parents were characterized to dissect the genetics underlying N response. The populations were evaluated in eight N-environments and genotyped using single-nucleotide polymorphism data derived from a genotyping-by-sequencing protocol to identify quantitative trait loci (QTL) associated with high NUE. Six QTL for NUE were identified on chromosomes 1D, 2D, 4A, 6A, 7A, and 7D that were associated with N use efficiency. The QTL on 2D and 4A co-localized with known loci governing photoperiod sensitivity and resistance to Fusarium head blight (caused by the fungal pathogen Fusarium graminearum Schwabe), respectively. Three of the identified QTL (6A, 7A, and 7D) were associated with NUE in previous investigations, while the QTL on 1D was novel. The final experiment employed a small panel of soft red winter wheat lines to study the effects of photoperiod alleles on chromosome 1D (Ppd-D1) on yield-related traits under three or five N rates that were variably split over two growth stages in eight environments. The results validated the effect of a photoperiod sensitive allele (Ppd-D1b) that was associated with increased grain yield across N rates in half of the Virginia testing environments and under low N rates in all Ohio testing sites at the expense of grain N content. Yield advantages conferred by the Ppd-D1b allele were attributable to increased floret fertility and kernel number per spike. The findings from these studies have direct application for winter wheat breeding programs targeting NUE improvements.
Doctor of Philosophy
Wheat (Triticum aestivum L.) products account for a significant percentage of the total dietary calories and protein consumed globally. To meet production demands, wheat requires efficient nitrogen (N) management to ensure continued grower profitability and to reduce negative environmental impacts of N lost from agricultural systems. This dissertation sought to evaluate variation among wheat lines for N use efficiency (NUE), assess the performance of wheat lines under multiple N supplies, validate traits that are associated with NUE, investigate the role of photoperiod sensitivity genes on N response, and identify regions of the wheat genome associated with high N use efficiency. These studies were conducted using panels of winter wheat lines grown under two or more N conditions over a combined 32 location-years. Results of Chapter I identified variation in cultivar response to N rates was more frequently observed when a greater number of N rates were used in trials of wheat N response. The first chapter also identified variation among wheat lines for NUE and identified lines that consistently produce high grain yields over N-location-years. In addition, above-ground biomass at physiological maturity was found to be strongly associated with grain yield under all N rates and was highly heritable in both studies. Chapter II utilized a combination of genetic and observable trait data to perform genetic analysis in two bi-parental populations grown in eight Nlocation-years. The study identified reproducible and significant genetic markers associated with NUE for application in wheat breeding programs. Upon analysis of photoperiod sensitive versus insensitive wheat lines in Chapter III, photoperiod sensitive wheat lines had a significant yield advantage under N-limited conditions in Ohio and across N treatments in half of the Virginia testing location-years. This resulted from an increased number of kernels per spike and fertile florets in photoperiod sensitive wheat lines. Results from this dissertation suggest that active breeding and selection for N response may be achieved through the employment of high NUE genes and the continued identification of adapted high NUE wheat parental lines.

As the first barrier to the external environment, the epicuticular waxes have a number of key roles in plant physiology. Although the wheat wild progenitors display a diversity of epicuticular wax phenotypes, the glaucous (visible wax) phenotype dominates cultivated varieties. However, the UK winter wheat variety Shamrock is unusual in that it exhibits a non-glaucous phenotype, conferred by the wild emmer gene Inhibitor of Wax 1 (Iw1). UK field trials with Shamrock associated a yield advantage of 4.15% with Iw1. This PhD tests the hypothesis that Iw1 imparts an advantage for wheat yield and physiology in the UK. Crossing Shamrock with six glaucous UK winter wheat varieties (Malacca, Alchemy, Hereward, Xi19, Robigus and Einstein) created non-glaucous near isogenic lines (NILs) with Iw1. NILs were grown at multiple field trial locations in the east of England over four years. A long-term shade trial reducing incoming light by 40 and 60% was also carried out in 2014. Yield, and various physiological components including water use efficiency (WUE) and spectral properties, were measured. Iw1 reduced flag leaf photosynthetically active radiation (PAR) reflectance by 15-40% and canopy reflectance by 12-20% (p<0.05). Despite this, Iw1 did not affect flag leaf PAR absorbance or canopy temperature, and conferred no advantage under long-term shading. Furthermore, there was no difference between NILs in photoinhibition following an extended period of high light stress. Iw1 did not affect WUE or yield. However, non-glaucous Hereward and Alchemy NILs yielded 4.96±1.15% (p<0.001) and 2.59±1.01% (p=0.045) more than their glaucous counterparts, although this advantage did not map to Iw1. Iw1 offered no advantage to UK winter wheat under normal UK growing conditions, nor under long-term shading. However, the yield advantage associated with the Iw1 introgression in Hereward and Alchemy is significant within a backdrop of plateauing wheat yields and worth pursuing.

The increasing concern of energy shortage and environmental pollution attracts worldwide exploration of using sustainable biomaterials for the production of biofuels and biochemicals. Utilising lignocellulosic raw materials for valuable bio-products production is generally considered as a preferred biosynthetic technology. Although various processes have already been proposed, lignocellulose hydrolysis is still remaining as one of the major challenges that prevents wide spread application of lignocellulosic raw materials in biofuel and biochemical production. The aim of this study was to investigate the feasibility of applying soft-rot fungi as a biological pretreatment of wheat straw for the generation of cellulase enzymes and then use the freshly produced enzymes to hydrolyse the fermented wheat straw to a sugar rich hydrolysate. The wheat straw hydrolysate had also been examined for the production of bioethanol and biochemicals, such as succinic acid and itaconic acid. Solid State Fermentations (SSF) of wheat straw were carried out using both Aspergillus niger and Trichoderma reesei. The fermentation conditions, such as moistures content, culture time, addition of nutrients, and modification of wheat straw were optimised for the production of cellulase. In a SSF using autoclaved wheat straw, an enzyme activity of 9.5 FPU/g was achieved. When 0.5% yeast extract and mineral solution were added, the enzyme activities increased to 24.0 FPU/g after 5 days of cultivation. In a SSF of an alkali soaked wheat straw (wheat straw treated with 1% NaOH at 25˚C for 24 hours), 21.8 FPU/g was obtained after just 1-day culture. Optimisation of hydrolysis process led to a hydrolysate containing 59.8 g/L glucose, which was achieved from the hydrolysis of biologically pretreated wheat straw at 18% solid loading, with an enzyme loading rate of 55 FPU/g at 50˚C. Fermentations using the wheat straw hydrolysate resulted in 28.6 g/L ethanol, which was equivalent to 93.4% of theoretic yield. Utilisation of wheat straw hydrolysate for succinic acid production was investigated using recombinant yeast strains. For Saccharomyces cerevisiae D2, the deletion of SDH1 and SDH2 genes enhanced succinic acid production by 68%. Optimisation of fermentation conditions and fermentation scales led to a succinic acid production to around 12 g/L, which was nearly 100-folds of what succinic acid production using the wild S. cerevisiae D2 strain at initial fermentation conditions. Use wheat straw hydrolysate to replace commercial glucose based semi-defined medium resulted in the same succinic acid production yield, but lower concentration due to the low sugar concentration in the hydrolysate. Biosynthesis of itaconic acid using wheat straw hydrolysate was also explored, but no significant itaconic acid production was observed.

ABSTRACT Triticum sphaerococcum (AABBDD, 2n = 6x = 42) is a land race of wheat known from the Indian subcontinent. It has several favourable characters including short and strong culms, hemispherical grains with a shallow crease (that may increase the yield of white flour), higher protein content compared to bread wheat (T. aestivum), and resistance to drought, and yellow rust caused by Puccinia striiformis. However, an unfavourable characteristic of T. sphaerococcum is its lower yield compared to bread wheat. Being a land race, the sphaerococcum wheat is poorly studied. This study was undertaken to increase knowledge of the physiology and genetics of this land race and determine if it may be possible to separate the favourable characters of T. sphaerococcum from its unfavourable characters. Plant height in bread wheat is controlled by many genes. ‘Reduced Height’ (Rht) genes which differ in their response to externally applied gibberellic acid (GA3) are responsible for the short stature of modern bread wheat varieties. Therefore, GA3 was used to probe the relationship between the semidwarf sphaerococcum phenotype and the Rht gene. T. sphaerococcum variety Sp5 showed a unique “seedling response” to externally applied GA3 when compared with T. aestivum varieties harbouring Rht1, Rht2, Rht8, Rht12, Rht13 or Rht18 alleles. A mapping population of doubled haploids was generated through wide hybridisation of F1 (Sp5 x Otane) with Zea mays. A genome-wide scan of Sp5 and Otane (parents) using 348 microsatellite (SSR) markers showed that only 169 of these markers (49%) were polymorphic between the parents. A DArT profiling yielded 348 markers that were polymorphic between the parents. Microsatellite markers and DArT markers were used to create a genetic map. The mapping population was phenotyped and a quantitative trait loci (QTL) analysis was performed for component traits of the complex sphaerococcum trait including plant height, spike length, awn length, yield, grain shape and crease size. Results of the QTL analysis indicated that it may be difficult to separate the favourable characters of T. sphaerococcum from its unfavourable characters through mutation because the component traits of the complex sphaerococcum trait may be under pleiotropic control of the Sp gene. The hypothesis that T. sphaerococcum originated through a mutation in T. aestivum was tested through induced mutation using gamma rays. Mutants from sphaerococcum-type to aestivum-type were isolated and phenotyped. Sphaerococcum-type mutants also were isolated and characterised from mutated aestivum-type wheat suggesting a possible origin of T. sphaerococcum through a mutation in T. aestivum.

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Dois experimentos (Exp. 1 e Exp. 2) foram conduzidos em condições de campo para determinar o desenvolvimento da brusone em espigas, bem como a performance fisiológica e produtiva das cultivares BR-18 (moderadamente resistente) e Guamirim (suscetível) inoculadas com Pyricularia oryzae e tratadas (+F) ou não (‒F) com o fungicida epoxiconazole (13,3%) + pyraclostrobina (5%). Relativo a Guamirim ‒F, BR-18 ‒F (efeito da resistência) resultou em redução de 44 e 64% na incidência final e severidade final, respectivamente, no Exp. 1, e 3 e 49%, respectivamente, no Exp. 2. Para a Guamirim +F (efeito do fungicida) houve redução de 65 e 77% na incidência final e severidade final, respectivamente, no Exp. 1, e 64 e 95%, respectivamente, no Exp. 2. Similarmente, houve redução maior que 75 % na taxa temporal de progresso no tratamento combinando a aplicação do fungicida e resistência de hospedeiro. Resultados obtidos na análise de regressão indicaram que a severidade encontrada nas espigas e folhas durante o período de 10-14 dias após a antese (daa) proporcionou uma maior perda de produtividade comparado a severidade encontrada aos 18-22 daa, e que a severidade da brusone nas espigas possui maior efeito negativo comparado a severidade encontrada nas folhas. Relativo a Guamirim ‒F, houve aumento de 0.3 e 16 % na produtividade dos grãos para BR-18 ‒F, 20 a 61% para Guamirim +F e 26 e 83% para BR-18 +F nos Exp. 1 e Exp. 2, respectivamente. Os tratamentos envolvendo aplicação do fungicida e cultivar resistente manteve a integridade das folhas (baseado em HAD, HLAI, HAA e HRI) e performance fotossintética (baseado em Fv/Fm, Fm, Y(II), e Y(NPQ)) das espigas e folhas em relação ao tratamento cultivar Guamirim ‒F. Em conclusão, os resultados do presente estudo sugerem que a integração do tratamento com fungicida e resistência de cultivar como prática de manejo para o controle da brusone em espigas. Adicionalmente, dois experimentos foram conduzidos em condições de casa de vegetação para avaliar as alterações associadas com a produção e particionamento de fotoassimilados entre a espiga e a folha bandeira em plantas de trigo infectadas com P. oryzae. Ambos experimentos foram inoculados aos 10 e 20 daa com suspensão de esporos de P. oryzae. Os resultados demonstraram uma redução dos parâmetros de fluorescência da clorofila a (Fm, Fv/Fm YII and Y(NO)) em folhas bandeiras e espigas infectadas associada a menor concentração de clorofila a + b, carotenoides e redução da capacidade de fixação do CO2 pela RuBisCO em folhas bandeiras infectadas. Em folhas bandeiras e grãos obtidos de espigas infectadas, houve redução na concentração de açúcares solúveis com um aumento da razão da concentração de hexoses sobre sacarose em folhas bandeiras. Em folhas bandeiras, houve menor atividade da sacarose fosfato sintase (SPS) e menor expressão do gene sacarose sintase associadas ao aumento da expressão e atividade das invertases. Estas alterações relacionadas a síntese e degradação da sacarose sugerem uma condição dreno dos tecidos foliares infectados. No estágio final de infecção ocorreu uma redução da concentração de amido nos grãos e aumento da sua concentração em folhas bandeiras. Adicionalmente, houve redução na atividade e expressão da ADP-glicose pirofosforilase associada com a menor expressão dos genes β- e α-amilase em folhas bandeiras e espigas. Em conclusão, os efeitos negativos da brusone na qualidade e produtividade dos grãos em trigo podem ser associados com alterações na produção e particionamento de carboidratos durante o processo de formação dos grãos.
Two field experiments (Exp. 1 and Exp. 2) were carried out to evaluate the spike blast development as well as the physiological performance and grain yield of wheat cultivars BR-18 (partially resistant) and Guamirim (susceptible) inoculated with Pyricularia oryzae and treated or untreated with the fungicide 13.3% epoxiconazole + 5% pyraclostrobin. Relative to Guamirim-untreated, BR-18-untreated (resistance alone) led to 44 and 64% control of final incidence and severity, respectively, in Exp. 1, and 3 and 49% control, respectively, in Exp. 2. Guamirim-treated (fungicide alone) led to 65% control of incidence and 77% control of severity in Exp. 1, and 64% control of incidence and 95% control of severity in Exp. 2. Similarly, there was reduction higher than 75 % in the temporal rate of spike blast progress when host resistance and fungicide were combined. Results from regression analyses indicated that spike and leaf blast severity at 10-14 days after anthesis resulted in greater yield losses (highest negative slope) than severity at 18 to 22 days after anthesis, and that spike blast severity had a greater negative effect on yield than leaf blast severity. Relative to Guamirim-untreated, there was a 0.3 and 16% increase in mean yield for BR-18-untreated (resistance alone), 20 and 61% increase for Guamirim treated (fungicide alone), and 26 and 83% for BR-18 treated (moderate resistance + fungicide) in Exp. 1 and 2, respectively. By virtue of their effects on blast severity, fungicide application and cultivar resistant resulted in higher measures of leaf health (mean HAD, HLAI, HAA and HRI) and photosynthetic performance (based on F v /F m , F m , Y(II), and Y(NPQ)) of both spikes and leaves than the untreated susceptible reference treatment. Results from this study suggesting that the integration of these strategies may be the best approach for managing spike blast and useful for future efforts to develop crop loss models and management guidelines for wheat blast. Additionally, two experiments were carried out in greenhouse conditions to assess the changes associated with photoassimilates production and their partitioning in source-sink relationship on flag leaves and spikes of wheat plants infected with Pyricularia oryzae. Flag leaves and spikes were inoculated at 10 days after anthesis (daa) (Exp. 1) and at 20 daa (Exp. 2) with a conidial suspension of P. oryzae. There was an impairment on chlorophyll a fluorescence parameters (analyzed by F m , F v /F m YII and Y(NO)) on the infected flag leaves and spikes coupled with reduced concentrations of chlorophyll a + b and carotenoids as well as lower capacity of CO 2 fixation by RuBisCO in the infected flag leaves. In these leaves and grains obtained from the infected spikes, there were lower concentration of soluble sugars and an increase on the hexoses to sucrose ratio on the flag leaves. In the infected flag leaves, there was a lower sucrose phosphate synthase (SPS) activity and lower expression of sucrose synthase (Susy) gene coupled with higher expression and activity of acid invertases. These alterations, associated with synthase and degradation of sucrose, suggestss a status sink in the infected flag leaves. At advanced stages of fungal infection, the concentration of starch was reduced on grains whereas on the infected flag leaves its concentration was kept elevated. There were reduction on the activity of ADP-glucose pyrophosphorylase and on the expression of ADP-glucose pyrophosphorylase genes and down regulation of β- and α-amylase expression at late stages of fungal infection on flag leaves and spikes. In conclusion, the greatest effect of blast on both grains quality and yield can be associated with alterations in the production and partitioning of carbohydrates during the grain filling process.

Considering the activity of introducing genetic resources with a high potential for yield, and with a wide adaptation range, it is possible to strengthen the cattle production system, through the production of adequate forage in quality, and quantity. Brazilian grass was introduced to Bolivia in 1974 for demonstrating excellent forage characteristics, and great adaptation qualities to the different ecosystems of the Andes. The material was introduced through the Experimental Station of Patacamaya, with their material supplied through the Experimental Station of Obonuco (Colombia). The following study was conducted at the Agropecuary Experimental Center of Condori, located 49 km. north of the city of Oruro, department of Oruro, and 12 km. northeast of the population of Caracollo. Geographically it is located between the parallels 17°31’41’’ latitude south, and 64°14’ 02’’ longitude west to the Greenwich, and at a height of 3830 m.a.s.l during the year of 2005. The study was performed with the objective of determining the apparent digestibility in Lamas feed with Brazilian grass, and with Wheat, for which 4 species between 2 to 3 years and an average weight of 79 were selected for the study. The specimens were selected according to phenotypic characteristics, each of them having their own metabolic cage with its own feeding and drinking station. The design was completely random with no structured treatments; the significant variables were evaluated under contrast test to 0.05 of probability. The obtained results regarding the quantity of food consumed is much related to the quantity of feces excreted without having statistical differences between these two variables, the average consumption being of 2157.8 g/day and the average production of feces of a 789.55 g/day. The consumption of water is statistically different but proportional to the amount of moisture found in the forage, meaning that the greater amount of water supplied through the plan the less the amount of drinking water. The species consuming Brazilian grass presented a water consumption of 244.64 cc/day in relationship to the moisture percentage of 11.51% of the plant, being 2.38% larger in comparison to wheat. The amount of feces produced by the experimental units shows no statistical difference at a 0.05 of probability in relationship to food consumption, meaning that the amount of feces produced is proportional to amount of ingested food. The urine volume registered 1540.32 cc/day in relationship with the consumption of Brazilian grass, and a lesser volume of 671 cc/day in relationship with wheat consumption, observing significance with 99% of reliability. The results of the digestibility of the nutrients in Brazilian grass, and wheat are the following: Protein 78.59% and 48.01%; Ash 72.99% and 52.59%; Fiber 47.70% and 52.51%; Ethereal Extract 62.64% and 53.11%, respectively. We can conclude that the Brazilian grass is an excellent forage specie of good digestible properties, being protein its principal digestible nutrient.

Generalment, el rendiment de blat es pot dividir en dos components principals: nombre de grans per m2 (GN) i pes mitjà del gra (AGW). El rendiment sol estar fortament associat amb GN, però també hi ha una relació negativa entre AGW i GN. Com que això pot representar una penalització en els guanys de rendiment assolibles si el creixement del gra està limitat per la força de la font, és important dilucidar si la reducció en AGW en resposta a augments en GN representa un cas de limitació per font, i reconèixer si AGW a germoplasma d'elit està limitat per la disponibilitat de recursos per omplir els grans. També, l'estrès per alta temperatura afecta negativament els dos components principals; GN i AGW al cultiu de blat. No obstant això, no és clar si la compensació reflectiria la competència entre grans en creixement. En aquesta tesi hem seleccionat i estudiat sota condicions contrastants de nitrogen un grup de cultivars de blat moderns per quantificar i analitzar les causes darrere de la relació entre GN i AGW. També, hem seleccionat dos genotips contrastants respecte a GN i AGW i vaig analitzar (i) en detall les causes de les seves diferències en AGW i (ii) les seves respostes de GN i AGW a l'estrès. Nostre resultat indica que la compensació entre AGW i GN a través del material d'elit és deguda principalment a diferències en el pes potencial intrínsec dels grans. També, la penalització d'AGW per estrès per altes temperatures post-antesi no va resultar de la competència pels recursos. Per tant, la reducció de AGW causada per l'estrès tèrmic en post-antesi podria haver estat deguda simplement a un efecte directe sobre el PGW per se. Quan es van imposar onades de calor transitòries tant en pre- com en post-antesi, la reducció d'AGW causada per l'estrès tèrmic en post-antesi va ser menor que amb el mateix tractament tèrmic post-antesi imposat únicament. Fins a cert punt, va haver-hi una mena d'efecte “priming” d'un estrès tèrmic anterior sobre la magnitud de l'efecte d'un estrès tèrmic subsegüent.
Generalmente, el rendimiento de trigo se puede dividir en dos componentes principales: número de grano por m2 (GN) y peso medio de grano (AGW). El rendimiento suele estar fuertemente asociado con GN, pero también existe una relación negativa entre AGW y GN. Como esto puede representar una penalización en las ganancias de rendimiento alcanzables si el crecimiento del grano está limitado por la fuerza de la fuente, es importante dilucidar si la reducción en AGW en respuesta a aumentos en GN representa un caso de limitación por fuente, y reconocer si AGW en germoplasma de élite está limitado por la disponibilidad de recursos para llenar los granos. Tambien, el estrés por alta temperatura afecta negativamente a ambos componentes principales; GN y AGW en el cultivo de trigo. Sin embargo, no está claro si la compensación reflejaría la competencia entre granos en crecimiento. En esta tesis hemos seleccionado y estudiado bajo condiciones de nitrógeno contrastantes un grupo de cultivares de trigo modernos para cuantificar y analizar las causas detrás de la relación entre GN y AGW. Tambien, hemos seleccionado dos genotipos contrastantes con respecto a GN y AGW y analicé (i) en detalle las causas de sus diferencias en AGW y (ii) sus respuestas de GN y AGW al estrés. Nuestro resultado indica que la compensación entre AGW y GN a través del material de élite debe haberse debido principalmente a diferencias en el peso potencial intrínseco de los granos. Tambien, la penalización de AGW por estrés por altas temperaturas post-antesis no resultó de la competencia por los recursos. Por lo tanto, la reducción de AGW causada por el estrés térmico en post-antesis podría haber sido simplemente debido a un efecto directo sobre el PGW per se. Cuando se impusieron olas de calor transitorias tanto en pre- como en post-antesis, la reducción de AGW causada por el estrés térmico en post-antesis fue menor que con el mismo tratamiento térmico post-antesis impuesto únicamente. hasta cierto punto, Hubo una especie de efecto “priming” de un estrés térmico anterior sobre la magnitud del efecto de un estrés térmico subsiguiente.
Generally, wheat yield can be divided into two main components; grain number per m2 (GN) and average grain weight (AGW). Yield is commonly strongly associated with GN, but there is also a common negative relationship between AGW and GN. As this may represent a penalty in achievable yield gains should grain growth be limited by the source strength, it will be important to elucidate whether the reduction in AGW in response to increases in GN represents a case of source-limitation, and to recognize whether AGW in elite germplasm is limited by resource availability to fill the grains. Also, heat stress negatively affects both main components; GN and AGW of wheat. However, it is not clear (i) whether the compensation would reflect competition between growing grains. In this thesis, we selected and studied under contrasting nitrogen conditions a group of modern wheat cultivars to quantify, and to analyze the causes behind, the relationship between GN and AGW. Also, we selected two contrasting genotypes regarding GN and AGW were selected from the previous study and analysed (i) in detail the causes for their differences in AGW and (ii) their GN and AGW responses to heat stress. Our result indicates that the trade-off between AGW and GN across elite material must have been mainly due to differences in the intrinsic potential weight of the grains. Also, the penalty of AGW by post-anthesis heat stress did not result from competition for resources. Therefore, the reduction of AGW caused by heat stress at post-anthesis might have been simply due to a direct effect reducing PGW per se. When transient heatwaves were imposed twice at both pre- and post-anthesis, the reduction of AGW caused by that post-anthesis heat stress was diminished compared with the effect of the same post-anthesis heat treatment imposed solely. To some extent, there was sort of a priming effect of an earlier heat stress on the magnitude of the effect of a succeeding heat stress.

Thesis (PhD(Agric) (Agronomy))--Stellenbosch University, 2008.
The adoption of the no-till planting method brought about changes to the way the wheat crop is established in the Mediterranean climate of the Western Cape. Row widths have to increase from the normal narrow rows (170-180 mm) to at least 250 mm to allow for sufficient stubble handling. Furthermore, planters are designed to place seed accurately in the soil at uniform depth, which may increase seedling survival rates. The main objective of this study was to determine the influence of the use of wide row widths on yield, the components of yield and grain quality parameters and to revisit planting density recommendations to be used with the notill planting method. On-farm, producer managed trials which included cultivars, row widths and planting density treatments were planted at Riversdale, Swellendam and Caledon in the Southern Cape region and at Moorreesburg and Hopefield in the Swartland during the 2004 to 2006 production seasons. All trials were factorial RCB designs with split-split plot arrangements. Grain yield, grain protein, hectolitre mass (HLM) and the yield components, seedlings m-2, seedling survival (%), number of heads m-2, number of heads plant-1, number of kernels head-1 and thousand kernel mass (TKM) were determined at all sites in 2005 and 2006. Seedling survival rates of 80% were easily achieved in all trials with the exception of Caledon and Swellendam in 2005. The no-till planting method may be efficient to improve on survival rates of 50-70% found with the conventional planting methods. The yield component response that raised the most concern was the clear trend of the reduction in the number of heads m-2 as row widths increased, which was significant in eight out of the nine experiments. The number of heads plant-1 decreased significantly as planting density increased in all experiments. Cultivars differed in the grain quality parameters grain protein (%) and HLM but were influenced minimally by the other treatments. Reductions in grain yield occurred in three out of eight trials in the Southern Cape and in three out of six trials in the Swartland, with reductions of between 6.8% and 33% in some seasons. The risk of yield loss due to wide row widths could not be excluded by this study and therefore the row widths used by producers should remain as narrow as practically possible. Grain yield response to increasing planting density differed between the two regions. No significant yield benefits were found in any of these trials if planting densities were increased above 175 target plants m-2. Planting densities may be reduced to between 70 and 87.5 kg seed ha-1 to achieve this target if the crop is planted in time and seedling survival rates of at least 80% can be achieved.

Increments en el rendiment de blat són necessaris per tal de fer front a la demanda creixent sota situacions complexes com la impossibilitat de expandir les terres cultivables, el canvi climàtic i el repte de produir grans mitjançant pràctiques agronòmiques sostenibles. En el passat, els guanys genètics s’han aconseguit optimitzant l’altura de la planta i el temps fins a antesi i, conjuntament amb la millora de la resistència al allitament i l’adaptació del blat, resultaven en increments importants del rendiment del gra. La millora genètica més enllà dependrà d’altres trets com la duració de cadascuna de les sub-fases del desenvolupament del blat o la combinació del nombre final de fulles i filocrons i els efectes en la fertilitat de les flors (un dels determinants més importants del nombre de grans i per extensió del rendiment). És per això, que aquesta Tesi es va centrar en la identificació dels trets en què es fonamenta el rendiment del gra i en debatre el compromís entre els diferents components fisiològics del rendiment del gra així com entendre l’efecte dels recentment identificats QTLs (locus de caràcters quantitatius) Eps en el desenvolupament del blat. El principal objectiu d’aquesta Tesi era millorar la comprensió dels trets responsables del rendiment del gra: com la distribució de les fases abans de floració, la fertilitat de l’espiga i la seva influència en el nombre de grans. Més particularment, identificar (i) els trets i les combinacions d’aquests que afecten al rendiment del gra, avaluant la possible variabilitat genètica en les fases abans de floració de les poblacions elit similars en temps fins a floració i en altura de planta; (ii) les funcions dels nous QTLs identificats, Eps-7D i Eps-2B en sub-fases particulars del temps abans d’antesi i fertilitat de l’espiga; (iii) la interacció de Eps-7D amb la temperatura i el fotoperíode sota condicions controlades. Per acomplir aquests objectius, es van dur a terme quatre assaigs de camp i un sota condicions controlades. Un gran nombre de poblacions bi-parentals derivades de progenitors elit van ésser avaluades en camp i es va seleccionar una mostra de línies amb altura de planta i temps fins a antesi similars per tal d’identificar els trets que en dirigeixen la variabilitat en rendiment. Les línies seleccionades presentaven una gran variabilitat en rendiment (c. 500-1000 g m-2) que es basaven en una millor fertilitat de l’espiga. Com que la major part de línies seleccionades amb un alt rendiment mostraven un nombre i un pes de grans elevat, podem concloure que la subsegüent millora del rendiment pot venir de l’augment en el nombre de grans sense implicar una reducció en el pes. L’avaluació de vuit línies que es diferencien en els Eps-7D i -2B en camp va revelar una interacció epistàtica entre ambdós, que afectava la dinàmica d’aparició de fulles, i el desenvolupament de les espiguilles i els primordis florals a més a més de les fases abans d’antesi. L’avaluació de Eps-7D en condicions controlades va revelar els efectes de la interacció entre aquest i la temperatura sobre les fases abans d’antesi i les dinàmiques de desenvolupament d’òrgans. La magnitud de l’efecte de Eps-7D era major que la de Eps-2B i els efectes de Eps-7D depenien de l’estat al·lèlic de Eps-2B. Les formes al·lèliques Eps-7D, Eps-7D-late i Eps-7D-early mostraven diferents graus de sensibilitat a la temperatura i les diferències en els seus efectes eren aparents en dies curts i a 9 ºC. Les conclusions d’aquesta Tesi van ser que el rendiment de gra pot millorar-se sense canviar el temps fins a antesi (optimitzant les fases d’abans d’antesi). Els Eps estudiats poden ser una eina per ajustar les fases d’abans d’antesi amb poques alteracions del temps fins a antesis. Aquí es demostra per primer cop la interacció entre dos Eps la qual només havia estat suggerida.
Los aumentos en el rendimiento del cultivo de trigo son fundamentales para satisfacer la creciente demanda en una situación compleja, con imposibilidades de expandir aún más las tierras cultivables, el cambio climático y el desafío de producir granos mediante prácticas agronómicas sostenibles. En el pasado, las ganancias genéticas obtenidas mediante la optimización de la altura de la planta y el tiempo hasta antesis, conjuntamente con la mejora de la resistencia al acame y la adaptación del trigo, resultaron en incrementos importantes del rendimiento del grano. Futuras ganancias genéticas dependerán de otros atributos como la duración de alguna sub-fase de desarrollo particular del trigo o la combinación del número final de hojas y filocronos y la fertilidad de las flores (uno de los determinantes más importantes del número de granos y, por ende, del rendimiento). Es por ello, que esta Tesis se centró en identificar los atributos en que se fundamenta el rendimiento del grano y en discutir las compensaciones entre los diferentes componentes fisiológicos del rendimiento del grano, así como comprender el efecto de los QTLs Eps recientemente identificados en el desarrollo del trigo. El principal objetivo de esta Tesis fue mejorar la comprensión de los atributos responsables del rendimiento del grano como la distribución de las subfases durante prefloración, la fertilidad de la espiga y su influencia en el número de granos. Particularmente identificar (i) los atributos y las combinaciones de estos que afectan al rendimiento del grano, evaluando la posible variabilidad genética en las fases prefloración de poblaciones élite que poseen similar duración hasta floración y en altura de la planta; (ii) las funciones de los nuevos QTLs identificados, Eps-7D y Eps-2B en sub-fases particulares de la duración tiempo preantesis y la fertilidad de la espiga; (iii) la interacción de Eps-7D con la temperatura y el fotoperíodo bajo condiciones controladas. Para cumplir estos objetivos, se llevaron a cabo cuatro ensayos de campo y uno bajo condiciones controladas. Un gran número de poblaciones bi-parentales derivadas de progenitores élite fueron evaluadas en condiciones de campo y se seleccionó una muestra de líneas con altura de planta y tiempo hasta antesis similares para identificar los atributos que determinan la variabilidad en el rendimiento. Las líneas seleccionadas presentaban una gran variabilidad en rendimiento (c. 500-1000 g m-2) que se pudieron explicar por un mayor peso de la espiga en antesis y mayor eficiencia de fructificación (ambos componentes del número de granos) determinadas en la fase reproductiva tardía. El aumento en el número de granos no redujo el peso de los granos, ya que dos tercios de las líneas presentaron un número de granos alto (alto rendimiento) también tuvieron un peso de grano más alto en comparación con aquellas con un número de granos bajo. La evaluación de ocho líneas que se diferenciaron en los Eps-7D y -2B en campo reveló una interacción epistática entre ambos, que afectaba la dinámica de aparición de las hojas, y el desarrollo de las espiguillas y los primordios florales. La evaluación de Eps-7D en condiciones controladas reveló los efectos de la interacción entre este y la temperatura sobre las fases preantesis y las dinámicas de desarrollo de órganos. La magnitud del efecto de Eps-7D fue mayor que la de Eps-2B y los efectos de Eps-7D dependían del estado alélico de Eps-2B. Las formas alélicas Eps-7D, Eps-7D-late y Eps-7D-early mostraron diferentes grados de sensibilidad a la temperatura y las diferencias en sus efectos fueron claramente demostradas en condiciones de días cortos y a 9 ºC. El trabajo realizado en esta Tesis contribuye a entender y mejorar aún más el rendimiento de grano en de trigo, ya que la variabilidad en algunas subfases de desarrollo en pre-antesis en la población estudiada (con un tiempo similar hasta antesis) presentó una variabilidad razonable para el rendimiento de grano. Además, la evaluación de combinaciones alélicas de dos Eps recientemente identificados y sus interacciones epistáticas ayudan a adaptar la combinación alélica para producir un fenotipo deseado con una distribución ventajosa del tiempo para fenofases importantes. La interacción entre dos Eps particulares es informado por primera vez en esta Tesis.
Increases in wheat yield are essential to meet the growing demand under a complex situation of impossibilities to further expand the arable lands, climate change, and the challenge to produce grains under environmentally friendly techniques. In the past, genetic gains were brought about by optimised plant height and time to anthesis which along with improving lodging resistance and wheat adaptation resulted in an important increase in grain yield. Further genetic gains will mostly depend on other traits, like the duration of particular sub-phases of wheat development or the combination of final leaf number and phyllochron and the effects on floret fertility (a major determinant of the number of grains, and hence grain yield). Therefore, this Thesis was focused on identifying traits underpinning the grain yield and discussing some important trade-offs between physiological components of grain yield as well as to understand the effect of newly identified Eps QTLs on wheat development. The main aim of the present Thesis was to improve the understanding of the physiological traits underlying grain yield such as distribution of pre-anthesis phases, spike fertility and their influence on grain number. Particularly to identify (i) traits and trait combinations that affect grain yield, evaluating possible genetic variability in pre-anthesis phases in elite lines with similar time to anthesis; and plant height; (ii) the functions of a newly identified Eps QTLs Eps-7D and Eps-2B beyond their known effect on time to anthesis such as their effect on the duration of individual pre-anthesis phases and spike fertility; and (iii) the interaction of the Eps-7D with temperature and photoperiod under controlled conditions. To accomplish these objectives, four experiments under field and one experiment under control conditions were performed. A large set of bi-parental population derived from elite parents were evaluated under field conditions and sub-set of lines with similar plant height and time to anthesis were selected to identify traits driving the grain yield variability in them. The selected lines carried large variability for grain yield (c. 500-1000 g m-2) which was explained better by spike dry weight at anthesis and fruiting efficiency, determined during late reproductive phase (traits that are components of grain number). Improving grain number did not reduce grain weight as two third of the lines presented high grain number (high grain yield) also had higher grain weight compared to those with low grain number. Evaluation of eight lines differing in Eps-7D and -2B under field conditions revealed an epistatic interaction between the two QTLs which affected the dynamics of leaf appearance, spikelet and floret primordia development in addition to the duration of pre-anthesis phases. Evaluation of Eps-7D under controlled conditions disclosed the interaction between Eps-7D × temperature on pre-anthesis phases and dynamics of organ development. Overall, the effect of Eps-7D was stronger than Eps-2B and the effects of Eps-7D depended on allelic status of Eps-2B. The allelic forms of Eps-7D, Eps-7D-late and –early, had different degree of sensitivity to temperature and the differences in their effect was clearer at 9 ºC under short day. The work reported in this Thesis may be useful in further improving grain yield in well adapted wheat regions, as the variability in individual pre-anthesis phases in the studied population with similar time to anthesis carried reasonable variability for grain yield. In addition, the evaluation of allelic combinations of two newly identified Eps and their epistatic interactions help in tailoring allelic combination to produce a desired phenotype with advantageous distribution of time to important phenophases. The interaction between two particular Eps is reported for the first time here which was only speculated before.

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Blast, caused by the fungus Pyricularia oryzae, has become an economically important disease in wheat. The objective of this study was to determine the effect of silicon (Si) on the photosynthetic gas exchange parameters (net CO 2 assimilation rate (A), stomatal conductance to water vapor (g s ), internal CO 2 concentration (C i ), and transpiration rate (E)) and chlorophyll fluorescence parameters (maximum quantum quenching (F v /F m and F v '/F m '), photochemical (q P ) and nonphotochemical (NPQ) quenching coefficients and electron transport rate (ETR)) in wheat plants grown in a nutrient solution containing 0 (-Si) or 2 mM Si (+Si) and inoculated with P. oryzae. The leaf Si concentration significantly increased for the +Si plants compared to the - Si plants and contributed to a decrease in the severity of blast symptoms. For the inoculated +Si plants, A was significantly higher at 72 (14%), 96 (12%) and 120 (58%) hours after inoculation (hai) when compared with their inoculated -Si counterparts. The g s and E were significantly higher by 60 and 42% at 120 hai for the inoculated +Si plants compared with the inoculated -Si plants, respectively. Significant differences between non-inoculated and inoculated plants were observed from 48 to 120 hai for A, g s and E and from 48 to 96 hai for C i . For the inoculated +Si plants, significant differences of F v /F m between the -Si and +Si treatments occurred at 48, 96 and 120 hai and at 72, 96 and 120 hai of F v '/F m '. The values of F v /F m significantly decreased by 1, 3 and 5% at 48, 96 and 120 hai, respectively, in the -Si plants compared with the +Si plants. Significant decreases of 10, 11 and 22% at 72, 96 and 120 hai, respectively, were observed for F v '/F m ' in the -Si plants when compared with the +Si plants. Significant differences between the non-inoculated and inoculated plants occurred from 48 to 120 hai for F v /F m and F v '/F m ', respectively. For the inoculated plants, significant differences between the -Si and +Si treatments occurred at 96 hai for both q P and NPQ and 72 and 120 hai for ETR. Significant differences between the non-inoculated and inoculated plants occurred at 120 hai for q P and at 96 and 120 hai for ETR. The total chlorophyll content (a + b) and the chlorophyll a/b ratio significantly decreased for the -Si plants compared with the +Si plants. The results of this study clearly demonstrate that the severity of blast symptoms decreased in wheat plants supplied with Si. These plants also exhibited improved gas exchange performance and less dysfunctions at the photochemical level.
A brusone, causada pelo fungo Pyricularia oryzae, tornou-se uma doença economicamente importante no trigo. Este estudo teve como objetivo determinar o efeito do silício (Si) sobre os parâmetros das trocas gasosas (taxa de assimilação líquida de CO 2 (A), condutância estomática ao vapor de água (g s ), a concentração interna de CO 2 (C i ) e taxa de transpiração (E)) e parâmetros de fluorescência da clorofila (eficiencia quântica máxima do fotosistema II (F v /F m e F v '/F m '), fotoquímica (q P ) e coeficiente de extinção não-fotoquimico (NPQ) e a taxa de transporte de eletrons (TTE)) em plantas de trigo crescendas em recipiente com solução nutritiva contendo 0 ou 2 mM de silício (Si) e inoculadas com P. oryzae. A concentração foliar de Si incrementou-se significativamente para plantas, contribuindo à dismunição da severidade da brusone. Para plantas inoculadas com +Si, A foi significativamente maior a 72 (14%), 96 (12%) e 120 (58%) hai do que em suas contrapartes inoculadas. A g s e E foram significativamente maiores em 60 e 42%, respectivamente, às 120 hai para as plantas inoculadas +Si em comparação com as plantas inoculadas -Si. Diferenças significativas entre as plantas inoculadas e não inoculadas ocorreu entre as 48 a 120 hai para A, g s e E e entre as 48 a 96 hai para C i . Para as plantas inoculadas +Si, diferenças significativas para F v /F m entre os tratamentos Si e +Si foram encontradas às 48, 96 e 120 dai e às 72, 96 e 120 hai para F v '/ F m '. Os valores de F v /F m diminuiram significativamente em 1, 3 e 5%, respectivamente, aos 48, 96 e 120 hai para plantas -Si, em comparação com as plantas de +Si. Reduções significativas de 10, 11 e 22%, respectivamente, às 72, 96 e 120 hai para F v '/F m ' ocorreu para as plantas -Si, em comparação com as plantas +Si. Diferenças significativas entre as plantas inoculadas e não inoculadas ocorreu às 48 a 120 hai para F v /F m e F v '/F m '. Para as plantas inoculadas, diferenças significativas entre os tratamentos -Si e +Si ocorreu apenas às 96 hai para ambos q P e NPQ e às 72 e 120 hai para TTE. Diferenças significativas entre as plantas inoculadas e não inoculadas só ocorreu em 120 hai para q P e às 96 e 120 hai para TTE. A concentração de clorofila total (a + b), e a razão de clorofil a/b diminuiu significativamente para as plantas -Si, em comparação com as plantas de +Si. Os resultados deste estudo demonstraram claramente que a severidade da brusone diminuiu em plantas de trigo supridas com Si em paralelo a um melhor desempenho das trocas gasosas e menores perdas disfuncionais ao nível fotoquímico.

Em diversos países, extensas áreas agrícolas são afetadas por inundações temporárias que ocasionam significativos prejuízos à produção de alimentos. Os objetivos deste trabalho foram: a) avaliar os efeitos da exposição de plantas de lentilha (Lens culinaris Medik) ao estresse por excesso hídrico em relação ao manejo do nível freático; b) avaliar o comportamento de cultivares de soja (Glycine max L. Merrill) a hipoxia e à aplicação de nitrogênio na atenuação dos danos ocasionados pelo excesso hídrico e c) avaliar as respostas de plantas de trigo (Triticum aestivum, L.) à saturação hídrica, total ou parcial, da camada de solo correspondente à zona radicular da cultura. Em plantas de lentilha, o excesso de água no solo reduziu a expansão foliar, o acúmulo de biomassa, a produção de grãos e reduziu a concentração de N, K, Ca, Mn e Mg nas folhas e intensificou o processo de senescência foliar. As taxas de ascensão e de rebaixamento do nível freático de 15 e 30 cm dia-1 influenciaram positivamente o desenvolvimento e a produção. Os danos mais drásticos foram ocasionados pela elevação e pelo rebaixamento do nível freático em 5 cm dia-1. O efeito negativo da inundação do solo na produção de grãos foi reduzido em 21% pelo aumento da taxa de ascensão e de rebaixamento do nível freático de 5 para 30 cm dia-1. A adição de 50 kg N ha-1 não minimizou os danos ocasionados pela hipoxia. Em soja, a área foliar, o acúmulo de matéria seca, a produção e a qualidade dos grãos dos cultivares decresceram com o prolongamento da inundação do solo. Os teores foliares de N, K, Mg e Mn decresceram linearmente e a concentração de Fe aumentou com a inundação do solo. O cultivar FT-Abyara apresentou maior crescimento vegetativo e o cultivar CD205 maior produtividade e maior teor protéico. Os maiores danos à produção foram ocasionados pela inundação do solo por período superior a 48 h. A aplicação de 50 e 100 kg N ha-1 aumentou o crescimento da parte aérea das plantas, a produção e a concentração de proteína dos grãos. O cultivar FT-Abyara apresentou melhores resultados à adição de N. A aplicação de N reduziu em 15% os danos causados pelo excesso de água no solo à produção de grãos. Em plantas de trigo, a saturação hídrica do solo intensificou a senescência das folhas, reduziu a produção de matéria seca, a taxa de crescimento da cultura e prejudicou a produção de grãos. Os efeitos ocasionados pela ocupação total dos poros do solo pela água foram mais severos para o desenvolvimento e a produção de grãos do que a saturação parcial dos poros pela água. O nível freático a 15 cm de profundidade minimizou em 30% os danos ocasionados pelo excesso de água no solo à produção de grãos. A aplicação de 50 kg N ha-1 reduziu em 16% os danos ocasionados pela saturação hídrica do solo à produção de grãos.
In many countries, extensive agricultural areas are affected by short-term waterlogging that cause significant damages to the crop yields. The objectives of this work were: a) to evaluate the stress effect of the soil water excess on lentil plants (Lens culinaris Medik) related to water table management; b) to evaluate the behavior of soybean cultivars (Glycine max L. Merrill) to hypoxia conditions and to the nitrogen supplying for reducing flood damages c) to evaluate wheat (Triticum aestivum, L.) responses to complete or partial soil water saturation in the root zone. On lentil plants the excess of water reduced the growth of the leaves, the dry matter and grain production and the concentration of N, K, Ca, Mn and Mg in leaves. Also the senescence process was increased. The elevation and lowering by 15 and 30 cm day-1 affected positively the crop development and yield production. The most severe damage was induced by rate elevation of 5 cm day-1 and drawdown of water table. The increasing of water table ascension and lowering rate from 5 to 30 cm day-1 alleviated the damage effect on grain production in 21%. Hypoxia injuries were not minimized by a supplemental addition of 50 kg ha-1 of nitrogen. The leaves area, shoot dry matter accumulation, the grain production and the grain protein concentration of soybean plants were reduced proportionally to the flooding duration. The N, K, Mg and Mn concentration in leaves decreased linearly while Fe concentration increased for the waterlogging duration. The soybean cultivar FT-Abyara showed the higher vegetative growth, while CD205 produced a greater grain yield and grain protein concentration. A flooding period of 48 h caused severe damage to grain yield. The leaf area, shoot growth, grain yield and grain protein increased with supplemental N application of 50 and 100 kg N ha-1. The soybean cultivar FT-Abyara showed the best results due to the nitrogen supply. The N addition reduced the grain production damages by 15%. In wheat plants, the water excess increased leaves senescence, reduced dry matter and the growth rate and produced a significant decreasing on grain weight. The effects caused by total water saturation of soil pores were more severe to the plant growth and grain yield than those caused by partial water saturation, even for large periods. A water table at 15 cm depth minimized by 30% the harmful effects of water excess to the grain production. The application of 50 kg N ha-1 reduced by 16% the damages on the crop yield caused by flooding.

In this study, Naegleria fowleri, a pathogenic amoeba and the causative agent of Primary Amebic Meningoencephalitis (PAM), was utilized to determine the presence or absence of classically conserved Golgi molecules featured in the expression of a Golgi apparatus. Previous studies concluded no Golgi expression via light microscopy and transmission electron microscopy, but a recent report on Naegleria gruberi indicated the presence of dispersed Golgi tubules. Non-pathogenic species of the Naegleria genus such as Naegleria gruberi 30540 and Naegleria lovaniensis 30569 were utilized in Western immunoblot analysis compared to reduced whole-cell lysate proteins of two strains of N. fowleri and Vero CCL-81, Chlorocebus sp. kidney epithelial cells, which were utilized as a positive control for Golgi expression. N. fowleri and N. lovaniensis whole-cell lysates had indications of a 110 kDa reduced protein, associated with the predicted molecular weights of the beta-COPI subunit of the COPI cis-Golgi vesicular transport complex with further Western immunoblot indication of a weak band around 25 kDa corresponding to rabbit polyclonal antibodies specific for ARF1. Serial Dilutions of Wheat Germ Agglutinin Alexa Fluor 488TM were performed on Vero cells, Naegleria fowleri 30894, and N. gruberi 30540 with 1:100 dilution of recommended stock dilution of WGA 488 determined for utilization in sequential immunofluorescence. Sequential immunofluorescence with Wheat Germ Agglutinin Alexa Fluor 488TM and then blocked with 3% BSA:PBS [wt/vol] dilution with subsequent incubation in rabbit anti-beta-COPI primary 1:250, and 1:1000 of Alexa Fluor 594 goat anti-rabbit secondary antibody exposure showed strong indications of organized cis- and trans-punctate Golgi body markers in close association in individual and dividing cells of Naegleria fowleri and conserved Golgi expression in the positive control Vero cells, but further experiments are necessary to verify this finding with N. fowleri.

The main objective of this thesis dissertation is functionally characterizing the genes involved in biotic and abiotic stresses of plants at molecular level. Previously, upon pathogen attack Rad6 gene expression was found to be changed in wheat and barley plants. To functionally characterize the Rad6 gene, VIGS (Virus induced gene silencing) system was used. HR (Hypersensitive response) like symptoms was detected in every silenced barley and wheat plants. To figure out, transcriptomes and proteomes of Rad6 silenced plants were analyzed. 2-D PAGE analysis was also performed on silenced and control wheat plants. No pathogen growth was observed in Rad6 silenced barley lines. Additionally, the susceptible wild type Arabidopsis plants showed resistant phenotype when any of the Rad6 gene copies is mutated. This suggests that Rad6 gene has a negative regulatory role in plant disease resistance which was proved for the first time. Yeast two hybrid protein interaction study suggests that RAD6 carrying out its function by interacting with SGT1 protein and regulating resistance related genes. It has been first time reported in this thesis that E2 (Ubiquitin conjugating enzyme) takes role in plant disease resistance. Boron which is the other consideration in the scope of thesis as an abiotic stress factor at a very limited amount is necessary for the normal development of plants. This study is conducted on highly boron tolerant Gypsophila perfoliata L. collected from a location in the boron mining area. The plant samples were tested in the presence of high boron (35 mg/kg) concentrations. The transcriptomes of the plant samples treated with the excess levels of boron to that of the samples grown under normal concentration were compared using differential display PCR method. Thirty bands showing differential expression levels at varying time points were analyzed. 18 of them were confirmed via qRT-PCR.

The provision of key text reading lists relies on students to select one they will utilise in undertaking a course. In anatomy and physiology an array of texts exist providing lecturers with the task of deciding the most suitable for inclusion within this list, the final choice for a student to undertake. Little evidence was found to identify the decision-making a student undertook in selecting a text. Based on disparate theoretical concepts an initial development of a conceptual process framework followed to provide a basis from which to identify influences which impacted on the student decision-making process. Using a mixed methods design a survey of students (N=964) undertaking anatomy and physiology courses was conducted whose results, following analysis provided the focus for in depth interviews. These included students (n=15), lecturers (n=3) authors (n=5) and publishers (n=2). Thematic analysis of the transcripts identified four overarching themes these being the Perception of the Textbook, Choice of the Textbook, Mismatch of Perceived Needs and Place of the Textbook. The results suggested two main influences which impacted on the student when choosing a text, those of existing prior knowledge and recommendation. Without prior knowledge, comprehension and cognition of the text was difficult. Recommendation by a lecturer or reading list, a strong influence, saw students selecting a recommended text without considering their own needs leading to an inability to use this. Without knowledge and recommendation students utilised aesthetic preference and heuristics in selecting a text, with many selecting additional texts to assist in using recommended texts. The results led to the development of the conceptual process framework indicating choice was a complex process for the student. Selecting a text is complex and affected by numerous influences. The study highlights a process through which a student traverses as they undertake the selection of their text. The study conclusions have led to the development of the Process Framework for Text Selection providing a novel and coherent linking of established theoretical concepts.

The provision of key text reading lists relies on students to select one they will utilise in undertaking a course. In anatomy and physiology an array of texts exist providing lecturers with the task of deciding the most suitable for inclusion within this list, the final choice for a student to undertake. Little evidence was found to identify the decision-making a student undertook in selecting a text. Based on disparate theoretical concepts an initial development of a conceptual process framework followed to provide a basis from which to identify influences which impacted on the student decision-making process. Using a mixed methods design a survey of students (N=964) undertaking anatomy and physiology courses was conducted whose results, following analysis provided the focus for in depth interviews. These included students (n=15), lecturers (n=3) authors (n=5) and publishers (n=2). Thematic analysis of the transcripts identified four overarching themes these being the Perception of the Textbook, Choice of the Textbook, Mismatch of Perceived Needs and Place of the Textbook. The results suggested two main influences which impacted on the student when choosing a text, those of existing prior knowledge and recommendation. Without prior knowledge, comprehension and cognition of the text was difficult. Recommendation by a lecturer or reading list, a strong influence, saw students selecting a recommended text without considering their own needs leading to an inability to use this. Without knowledge and recommendation students utilised aesthetic preference and heuristics in selecting a text, with many selecting additional texts to assist in using recommended texts. The results led to the development of the conceptual process framework indicating choice was a complex process for the student. Selecting a text is complex and affected by numerous influences. The study highlights a process through which a student traverses as they undertake the selection of their text. The study conclusions have led to the development of the Process Framework for Text Selection providing a novel and coherent linking of established theoretical concepts.

Nos connaissances sur la résilience (résistance à la dégradation et capacité de rétablissement) des pelouses tropicales anciennes restent limitées par rapport à nos connaissances sur les pelouses tempérées. Bien que très résilientes aux perturbations endogènes telles que le feu, la dynamique de la végétation dans les pelouses tropicales sujette au feu semble être freinée par les perturbations anthropiques, en particulier la dégradation du sol. Après la perturbation du sol, le pool interne d’espèces (i.e. la végétation restante et la banque de graines) est souvent réduit et parfois absent, et le rétablissement naturel dépend principalement de la dispersion des graines à partir des sites alentours via la pluie de graines. Cependant, les communautés végétales des zones dont le sol a été perturbé peuvent rester très différentes des sites de référence de nombreuses années après la dégradation, avec pratiquement aucun rétablissement de la végétation naturelle. Bien qu’extrêmement pertinente, la dynamique de dispersion des graines et la résilience des pelouses tropicales anciennes après la perturbation du sol restent très peu étudiées. Dans cette thèse, j'ai effectué une synthèse bibliographique et trois études expérimentales sur la dynamique de la pluie de graines et sur l'enlèvement des diaspores dans les pelouses. J'ai d'abord effectué une revue systématique de la littérature sur les études de pluie de graines dans les pelouses du monde. J'ai (1) évalué où, comment et pourquoi des recherches sur la pluie de graines ont été menées ; (2) examiné la manière dont la conception méthodologique et les résultats ont été rapportés ; et (3) fourni des lignes directrices pour les recherches futures sur la pluie de graines dans les pelouses. J'ai trouvé un déséquilibre remarquable dans le nombre d'études entre les types de pelouses, qui devient encore plus dissemblable d'une plage climatique à l'autre lorsque le domaine couvert par chaque type de pelouse est pris en compte. J'ai identifié d'importantes lacunes dans les connaissances dans la recherche sur la pluie de graines des pelouses. J'ai également constaté une grande disparité entre les méthodes et les données présentées dans les différentes études. De plus, j’ai constaté que seules quelques tentatives avaient été faites pour évaluer l’efficacité des pièges à graines et qu’aucune étude à ce jour n’a proposé de protocole pour évaluer l’efficacité des méthodes de tri des graines. Ensuite, je mène une expérience sur le terrain pour proposer un protocole standard simple permettant d’évaluer l’efficacité de deux types de pièges à graines (pièges collants et entonnoirs) et une méthode de tri des graines permettant d’évaluer l’efficacité des méthodes avant les études de pluie de graines. Les deux derniers chapitres concernent la dynamique de la pluie de graines et de l’enlèvement secondaire des diaspores dans des zones préservées et dégradées par l’exploitation de gravier pour la construction de routes dans la végétation de campo rupestre, une pelouse édaphique mégadiverse du sud-est du Brésil. Le petit nombre de graines récoltées à partir de la pluie de graines indique la limitation des graines et suggère une relation de cause à effet étroite entre la limitation de la dispersion des graines et la faible résilience après perturbation du sol. L’identification de quelques espèces relativement abondantes dans la pluie de graines place ces espèces en tant que bonnes cibles pour la réintroduction dans futurs projets de restauration. Les perturbations ont modifié l'identité des fourmis en interaction avec les diaspores, ce qui a entraîné des résultats contrastés des interactions fourmis - diaspores
Our knowledge of tropical old-growth grassland resilience (i.e. resistance to degradation and capacity for recovery) remains limited relative to our knowledge of temperate grasslands. Although highly resilient to endogenous disturbances such fires, the vegetation dynamics in old-growth fire-prone tropical grasslands seems hampered by anthropogenic disturbances, especially topsoil degradation. After topsoil disturbance, the internal species pool (i.e. remaining vegetation and the seed bank) is often depleted or even absent, and natural regeneration depends mainly on seed dispersal from surrounding sites via the seed rain. However, plant communities on areas disturbed by soil removal can remain very different from preserved sites many years after degradation, with almost no recovery of the natural vegetation. Despite extremely relevant, seed dispersal dynamics and resilience of tropical old-growth grasslands after soil disturbance remains much overlooked. In this thesis, I carried out a review and three experimental studies about seed rain and diaspore removal dynamics in grasslands. In CHAPTER1, I did a systematic literature survey about seed rain studies in global grasslands. I (1) assessed where, how and why research on seed rain has been carried out; (2) examined how methodological design and results have been reported; and (3) provided guidelines for future research on seed rain in grasslands. I found a remarkable unbalance in the numbers of studies between grassland types, which becomes even more dissimilar across global climatic ranges when the area covered by each grassland type is take into consideration. I identified significant knowledge gaps in grassland seed rain research. I also found a great disparity of methods and data being reported across studies. Additionally, I found that only a few attempts have been made to assess the seed trap efficiency and no studies to date have proposed any protocol to evaluate the effectiveness of seed sorting methods. Then, in CHAPTER 2, I ran a field experiment to propose a simple standard protocol to evaluate the efficiency of two seed trap types (sticky and funnel traps) and of a seed sorting method to assess the efficient of the methods prior to seed rain studies. As a case of study, in CHAPTER 3 and 4, I studied seed rain and secondary diaspore removal dynamics in preserved areas and in areas degraded by gravel exploitation for road construction in campo rupestre vegetation, a megadiverse edaphic grassland in southeastern Brazil. The small number of seeds captured in the seed rain, indicates seed limitation and suggests a close causal relationship between seed dispersal limitation and the low resilience after soil disturbance. The identification of some relatively abundant species in the seed rain places these species as good targets for reintroduction in future restoration projects. Topsoil removal changed the identity of ants interacting with diaspores, resulting in contrasting outcomes from ant-diaspore interactions. The lack of diaspore removal towards degraded areas indicates that establishment limitation is a factor hampering natural regeneration. Our findings help to explain, at least partially, why natural regeneration is compromised after soil removal, which strongly influences diaspore fate and interactions with potential ground-dwelling dispersers, resulting in different ecological outcomes and strong influencing vegetation dynamics and regeneration. I expect that these results will guide future research on seed dispersal and resilience in grasslands, underpinning decisions on restoration and conservation practices on these threatened environments
O nosso conhecimento sobre a resiliência (isto é, resistência à degradação e capacidade de recuperação) de savanas tropicais permanece muito aquém do nosso conhecimento já adquirido sobre as savanas temperadas. Savanas tropicais, embora altamente resilientes à perturbações endógenas, como o fogo, se mostram extremamente vulneráveis à certas perturbações antrópicas como a degradação do solo, a quais podem ocasionar drástica alteração da dinâmica da vegetação. Após a perturbação da camada superficial do solo, o conjunto interno de espécies (isto é, a vegetação remanescente e o banco de sementes) são frequentemente reduzidos ou até mesmo completamente eliminados. Nestes casos, a regeneração natural depende principalmente da dispersão de sementes da vegetação do entorno através da chuva de sementes. No entanto, comunidades vegetais em áreas perturbadas pela remoção do solo podem permanecer, mesmo após vários anos ao distúrbio original, muito diferentes do ecossistema de referência, apresentando baixíssima capacidade de regeneração natural. A dinâmica de dispersão de sementes em savanas tropicais, apesar de extremamente relevantes para uma melhor compreensão sobre a resiliência desses ecossistemas frente a ações antrópicas, permanece pouco estudada. Nesta tese, realizei uma revisão e três estudos experimentais sobre a dinâmica da chuva de sementes e da remoção de diásporos no campo rupestre, uma savana tropical natural, megadiversa e muito antiga localizada no sudeste do Brasil. No primeiro capítulo, realizei uma pesquisa bibliográfica sistemática sobre estudos de chuva de sementes em áreas não florestais no mundo com os seguintes objetivos: (1) avaliar onde, como e por que as pesquisas sobre chuva de sementes foram realizadas; (2) examinar como o desenho metodológico e os resultados foram relatados; (3) fornecer diretrizes para futuras pesquisas sobre chuva de sementes em áreas não florestais. Nesta revisão, eu encontrei um notável desequilíbrio no número de estudos entre os tipos diferentes tipos de áreas não florestais, o qual se torna ainda mais notável em relação à distribuição dos estudos entre as faixas climáticas globais e em relação à área total recoberta por cada ecossistema (ex. savanas tropicais). Neste estudo, foram identificadas algumas importantes lacunas de conhecimento relativas a estudos sobre a chuva de sementes em áreas não florestais. Foi evidenciado também uma grande disparidade entre os métodos de estudo de chuva de semente e sobre a maneira de reportar os dados observados, o que dificulta comparações entre estudos. Verificamos que apenas algumas tentativas foram feitas para avaliar a eficiência das armadilhas de captura de sementes e que nenhum estudo até o momento propôs algum protocolo para avaliar a eficácia dos métodos de captura de sementes utilizando armadilhas de sementes para áreas não florestais. No segundo capítulo, foi proposto e testado um protocolo simples para avaliar a eficiência de dois tipos de armadilhas de sementes (armadilhas pegajosa e de funil) e a eficácia de um método de busca e triagem de sementes coletas em armadilhas de funil, os quais podem ser realizados previamente aos estudos de chuva de semente. Como casos de estudo, no terceiro e quarto capítulos, pesquisei a dinâmica da chuva de sementes e de remoção secundária de diásporos em áreas preservadas e em áreas degradadas pela exploração de cascalho para a construção de estradas na vegetação do campo rupestre. O pequeno número de sementes capturadas na chuva de sementes indica limitação na dispersão de sementes e sugere uma estreita relação causal entre a limitação de dispersão de sementes e a baixa resiliência observada nestas áreas degradadas após a perturbação do solo.A identificação de espécies relativamente abundantes na chuva de sementes coloca essas espécies como potenciais alvos para futuros projetos de restauração visando a reintrodução de espécies

Contexte. Chez l’homme, la mise en bouche d’un aliment est l’étape ultime de la chaîne alimentaire et le début du processus de dégradation et de digestion. Avec l’âge la santé orale évolue et peut parfois rendre l’acte alimentaire difficile.Objectif. L’objectif de cette étude est de déterminer les facteurs (salivaire, dentaire, musculaire) impactant sur les dimensions physiologiques (faculté à former un bol alimentaire, libération et perception de la flaveur) de l’acte alimentaire et/ou la prise alimentaire et la corpulence des séniors. Ceci permettra de d’identifier des techniques culinaires permettant d’adapter la texture des aliments aux problèmes bucco-dentaires.Matériel et méthode. 108 séniors (>65 ans) vivant à domicile et ne présentant pas de pathologie chronique ont été recrutés et caractérisés sur la base des dimensions suivantes : santé orale (examen clinique), auto-évaluation de la santé orale, perceptions sensorielles, faculté à former un bol alimentaire, comportement alimentaire, état de santé général. En parallèle, des techniques culinaires permettant d’améliorer la texture de la viande ont été testées. Leur efficacité a été évaluée via des mesures rhéologiques et la perception du confort en bouche par les séniors eux-mêmes.Résultats et conclusion. L’analyse multidimensionnelle des données montre que les facteurs de santé orale (dentition, salivation, force musculaire) jouent des rôles différents dans les processus de mastication et de prise alimentaire chez les personnes âgées. De plus, l’étude du confort en bouche a permis de sélectionner des techniques culinaires optimisant la tendreté et la jutosité de la viande. Ces résultats permettront de développer une offre alimentaire adaptée aux troubles oraux survenant avec l’âge
Context. In human, oral food intake is the ultimate stage of food supply chain and the beginning of food disintegration and the digestion process. During aging, the oral health changes and sometimes eating food can be a real challenge as food can be hard to masticate, humidify or swallow.Objective. The aim of the present study is to determine which oral factors (salivary, dental, tongue strength) have an impact on physiological – ability to form a food bolus – and psychological – pleasure to eat – dimensions of food oral processing in order to select culinary techniques and help elderlies maintaining an appropriate protein intake in spite of the occurrence of poor oral health.Material and method. Resting and stimulated salivary flow, oral status, the ability to form a food bolus, the pleasure induced by food consumption and the nutritional status were measured on 108 elderly people (65-92 years old, living at home, with no acute pathology at the time of the study). In parallel, culinary technics that aimed at improving meat texture were developed and evaluated throughout physical measurements and oral comfort assessment by the elderly volunteers.Results and conclusion. Multivariate analysis highlighted the fact that oral factors (salivary, dental, muscular) play different roles in food oral processing and eating behavior in elderly people. Moreover, the assessment of oral comfort on the culinary technics showed that some technics improve significantly meat tenderness and juiciness. Those results will help the development of food offer tailored to elderly people with or without oral health impairments

La septoriose (pathogène Zymoseptoria tritici) est la plus importante maladie foliaire des cultures de blé en Europe. Les méthodes de lutte comprennent la résistance variétale, les stratégies d’évitement de la maladie et le recours aux fongicides. Cependant, ces stratégies n’assurent pas une protection complète des cultures de blé. La tolérance à la septoriose est une approche complémentaire qui vise justement à maintenir le rendement en présence de symptômes. La tolérance à la septoriose dépend de traits physiologiques de la plante et d’équilibres source/puits : la demande des puits (croissance des grains) doit être satisfaite malgré une disponibilité réduite des sources (capacité photosynthétique réduite par les symptômes foliaires). La surface verte du couvert, la sénescence et les composantes du rendement sont des traits potentiels de tolérance intéressants qui ont été étudiés lors de ce projet. Une étude de datamining, une expérience en serre et deux expériences au champ ont été menées pour fournir des informations complémentaires sur les mécanismes de tolérance à la septoriose. Les effets des interactions génotype × environnement sur les traits de tolérance ont été étudiés pour deux saisons × cinq localisations × neuf cultivars. La nutrition azotée et le métabolisme de quatre lignées double-haploïdes (DH, contrastées du point de vue de leur tolérance à la septoriose) ont été examinés dans une expérience en conditions contrôlées à l'UMR ECOSYS (INRA, AgroParisTech Grignon, France). Les bilans source/puits de six lignées DH contrastant pour la tolérance ont également été examinés en fonction de leurs réponses à un traitement d'égrainage, appliqué dans une expérience au champ à Hereford (Royaume-Uni). Enfin, une expérience au champ avec deux stratégies fongicides (contrôle total des maladies / lutte contre les maladies non-ciblées) a permis d’étudier la tolérance à la septoriose de six cultivars modernes (Leicestershire, Royaume-Uni). L'objectif principal était de vérifier les traits potentiels de tolérance à la septoriose sur des cultivars actuellement commercialisés. Des traits potentiels de tolérance à la septoriose ont été identifiés tels que la date d’épiaison, le faible degré de limitation des puits par les sources lors de la phase de remplissage du grain des couverts sains, la distribution verticale des surfaces foliaires favorisant des feuilles supérieures relativement grandes. Les résultats ont montré que ces caractères pourraient être sélectionnables, sans compromis avec le rendement potentiel. Enfin, le projet a également discuté du besoin de méthodes alternatives de quantification de la tolérance du blé à la septoriose, ainsi que de l'importance des variations environnementales qui doivent être prises en compte pour étudier les variations génétiques de la tolérance, mais qui pourraient également être utilisées pour identifier des environnements tolérants
The Septoria tritici blotch disease (STB, pathogen Zymoseptoria tritici) is the most damaging foliar infection of wheat crops in Europe. Disease management strategies include cultivar resistance, disease escape strategy and fungicides. However, these strategies have failed to provide a complete protection of wheat crops. The STB tolerance is a complementary approach which aims to maintain yield in the presence of the symptoms. The tolerance of STB relies on plant physiology and source/sink balance: the sink demand (the grain growth) must be satisfied in spite of reduced source availability (photosynthetic capacity as affected by the STB symptoms on the leaves). The green canopy area, the senescence timing and the grain yield components are interesting potential sources of tolerance that were studied in this project. A data-mining study, one glasshouse experiment and two field experiments were carried out providing complementary insights on STB tolerance mechanisms. The genotype × environment interaction effects on tolerance traits were investigated for two seasons × five locations × nine cultivars datasets. The nitrogen nutrition and metabolism of four doubled-haploid (DH) lines contrasting for STB tolerance were examined in a controlled-glasshouse experiment at UMR ECOSYS (INRA,AgroParisTech) Grignon, France. The source/sink balance of six DH lines contrasting for STB tolerance was also examined according to their responses to a spikelet removal treatment, applied in a field experiment in Hereford, UK. Finally, a field experiment with two fungicide regimes (full disease control and non-target (STB) disease control) probed the STB tolerance of six modern UK winter wheat cultivars in Leicestershire, UK. The main objective was to verify identified potential STB tolerance traits in commercial cultivars. Putative STB tolerance traits have been identified such as the early heading date, the low degree of grain-source limitation of healthy crops during the grain filling phase, the vertical canopy distribution favouring a relatively larger flag-leaf. Results showed these traits might be selectable in wheat breeding without a trade-off with the potential yield. Finally, the project also discussed the need for alternative STB tolerance quantification methods, as well as the importance of environmental variations which have to be taken into account to study genetic variation in tolerance, but which could also be used to discriminate tolerant environment