No description available.

No description available.

No description available.

The Green Revolution introduced wheat varieties containing semi-dwarfing genes (Rht) that encode gibberellin (GA)-insensitive forms of the growth-repressing DELLA proteins, conferring improved resistance to lodging and improved harvest index. Reduction in the use of nitrogen (N) fertilizers is required to minimise environmental damage. Since most Rht varieties have been selected under high N inputs, new semi-dwarfing alleles may need to be developed. The response of tall, semi-dwarf and dwarf lines of wheat to N rate was examined in the field, but failed to provide evidence of higher N -responsiveness of rht tall varieties compared to Rht-1 semi-dwarfs and dwarfs. Expression of GA biosynthetic and signalling genes was monitored in elongating stems in field and controlled environment conditions under different N and water regimes. Although peduncle GA levels were reduced under N stress, there was no evidence that the effect of N supply on stature was directly mediated by changes in the transcription level ofGA metabolic genes. GA-biosynthetic genes were assessed as novel sources of dwarfism that may respond differently to environmental stresses such as N supply. A number of TILLING lines carrying mutations in the three homoeologues of GA20ox1 were crossed in order to generate combinations of mutant alleles. Triple knock-out plants from four combinations of alleles were identified by KASP genotyping assay in the F2 generation and all plants from the segregating populations were assessed for final height. There was a correlation between the genotypes and height, with triple knockouts being the shortest and wild types the tallest. Data from an F 3 population of the a1b.b1b.d1c genotype confirmed this observation and showed that reduced-height mutants maintained the same grain size and number as the wild-type plants. Therefore GA200xi may be classified as a novel wheat semi-dwarfing gene with potentially beneficial effects on height reduction without negatively affecting yield.

Zymoseptoria tritici is an important foliar pathogen of Triticum aestivum (cultivated wheat). Control of Septoria tritici blotch disease in the field, caused by Z. tritici, is mainly facilitated by fungicidal chemical applications and planting of wheat breeds containing a combination of Septoria resistance loci (STB loci). Currently, molecular mechanisms underlying STB trait resistance are not fully understood and efficacy and availability of chemical fungicides is limited. In order to improve control of this disease in the field requires greater understanding of the processes underlying successful wheat infection. Secreted "effector" proteins enable plant pathogenic fungi to manipulate host defences for successful infection. Characterisation of effector proteins, demonstrating an important function during wheat infection may provide a novel approach to developing new disease control strategies, as well as aiding in our understanding of disease dynamics. Secreted Lysin Motif-containing (LysM) proteins are now well-known effector molecules deployed by fungal pathogens, as originally defined for the Extracellular protein 6 (Ecp6) gene in Cladosporium fulvum. Using homology and in silico analysis three putative LysM containing secreted effector genes were identified in the Zymoseptoria tritici genome. Gene sequencing analysis confirmed they are highly conserved in multiple Z. tritici isolates. Expression analysis indicates two of these genes, Mycosphaerella graminicola 1LysM (Mg1L) and Mycosphaerella graminicola 3LysM (Mg3L), are highly expressed during symptomless wheat infection. Collaborative protein functional analysis indicates a role in chitin-binding and protection against plant defence compounds for Mg1L and Mg3L. Mutational analysis indicates that Mg3L in particular, plays an essential role during Z. tritici wheat infection. This represents the first fully characterised effector protein in Z. tritici and emerges alongside functional characterisation of LysM effector proteins in other plant pathogenic species e.g. Magnaporthe oryzae Secreted LysM Proteinl (Slp1). Mg3L protein orthologues are found in many plant pathogenic ascomycete fungal genomes and two plant pathogenic oomycete genomes.

The effects of crop plant height, relative time of weed emergence (RTE) and crop seed vigour and dormancy on the ability of Rht (Reduced height) lines of winter wheat to maintain yield and suppress weeds, were investigated. Near Isogenic Lines (NILs) of Rht lines in Mercia cultivar background were planted with oat as a model weed. As NILs were genetically similar apart from the Rht genes, actions and interaction of RTE and crop height were assessed without confounding effects of other traits associated with competitive ability. Seed vigour and dormancy were included in case they influenced RTE. In competition with oat, the crop yield increased and yield losses decreased as the oat emergence was delayed. The yield loss was greater in the dwarf NILs (Rht-Bl c: 49% and Rht12: 64%) compared to the Mercia control (18%) and semi-dwarfNILs (25%). RTE had no effect on crop height or biomass or light interception in both the years. Yield increased linearly with the crop height both in the presence and absence of weeds. Weed-free yields were always exceeding the weedy yields irrespective ofRTE. Whether the Rht lines were sensitive or insensitive to gibberellins, did not make any difference to yield maintenance and weed suppression, but their weed suppressive ability was generally poor. High vigour cv. Mercia and Rht-Bl c seed lots competed better against weeds than low vigour ones, but the effect related to a ,higher crop plant population as the effect of R TE of weeds was the same for low and high vigour lots. The acquisition of germinability and dormancy during maturation of grams and subsequent field emergence was studied in 19 winter wheat NILs in cv. Mercia, Maris Huntsman and Maris Widgeon backgrounds. High levels of dormancy were found in the dwarf allele Rht-Bl c in all three backgrounds and also in Rht-Dl b + Rht-Bl c in Maris Huntsman and Maris Widgeon backgrounds. Longer mean time of emergence, lower percentage of emergence, shorter coleoptile length, higher Hagberg Falling Number and GA insensitivity were the causes for the delay in emergence which slightly reduced the ability of Rht-Blc and Rht-Dlb+Rht-Blc to compete against weeds. Upright with erect leaf NIL's early season height, maximum height were positively correlated with grain yield and weed suppression, and negatively correlated with crop yield loss and weed seed production. Overall, crop height was found to be more important in achieving weed suppression than relative time of weed emergence.

Human induced climate change is predicted to increase mean surface air temperature by 2 to 4 degrees C with significant drying in some regions by the end of this century which will affect wheat production and billions of people who depend on the crop for their livelihood. Factorial pot experiments were conducted to compare the responses of GA-sensitive and GA-insensitive reduced height (Rht) alleles in wheat for susceptibility to heat and drought stress during booting and anthesis. Grain yield, grain set (grains/spikelet) and grain quality of near-isogenic lines (NILs) were assessed following three day transfers to controlled environments imposing day temperatures from 20 to 40 degrees C at the Plant Environmental Laboratory (PEL), University of Reading, UK.

Four glasshouse experiments examined salinity stress and tolerance in wheat. The first experiment examined the responses of three wheat cultivars from Saudi Arabia (Local wheat, West bread and Yecora Rojo) and two UK wheat cultivars (Paragon and Belvoir) to different levels of salinity (Tap water, 25, 50, 100, 150 and 200 mM NaCI). In the second experiment, Yecora Rojo and Paragon were selected to test whether improved wheat tolerance to salinity could be obtained by applying exogenous Salicylic acid (0, 0.5, 1 and 2 mM SA) via priming seeds for 6 hours. The third experiment further tested the effect of SA on tolerance to salinity with SA applied through seed soaking for 6h and 24h. Two salinity tolerant cultivars (S24 and Sakha 93) were included for comparison. The fourth experiment compared the effect of SA applied by seed soaking (6h) or by foliar spray. In all experiments, saline conditions gave significant declines in wheat growth parameters, gas exchange, yield and yield components with increases in salinity concentration, whereas protein and chlorophyll content increased. Cultivar Paragon grew significantly better than cultivar Yecora Rojo in non-saline conditions but not under salinity stress. Treating wheat with SA produced only a minor improvement in growth parameters, yield and yield components under salinity stress. Compared to salt tolerant cultivars, Paragon showed significant response to SA in most variables. The influence of SA depended on genotype, plant stage and SA concentration more than soaking time and application method with 0.5 and 1 mM SA concentrations being the most effective. SA mitigates but does not prevent salinity impacts and has a dual function which can give positive or negative effects under salinity stress.

The effect of natural and simulated rainfall during seed development and maturation on wheat (Triticum aestivum L.) seed quality development, particularly changes in subsequent air-dry longevity (stored hermetically at 40°C with 15% moisture content), was investigated in poly-tunnel (2010) and field experiments (2011 and 2012). Avoiding rain during seed development and maturation accelerated the rate and reduced the duration of seed filling and thus reduced final seed weight, while increase in rainfall slowed down the rate and increased the duration of seed filling and increased seed weight in wet and cold weather (2011), but dry and warm weather (2012) had the opposite effect. Maximum germination of seeds dried after harvest was attained at 39-49 days after anthesis (DAA) and maintained throughout until 70 DAA. Seeds not dried attained ability to germinate slightly later with subsequent fluctuations, probably associated with dormancy. Potential longevity increased during this period, reaching a maximum at 53-56 DAA, coinciding with harvest maturity, and then declining in 2012 but not in 2011. Wetting ears reduced longevity at all stages of seed development when seeds were harvested soon after the event, and more so after two wettings, but considerable recovery in subsequent longevity occurred when seeds were harvested after 1 or 7 days re-drying after wetting. Reduction in rainfall significantly reduced crude protein and the incidence of blackpoint in both years. Hagberg Falling Number (HFN) decreased in 2011, but increased in 2012, perhaps due to wetter and cooler conditions in 2012. Rainfall affected seed quality development but the extent of damage varied amongst developmental stages, being greater at later developmental stages although considerable ability for recovery with re-drying was noted. Rainfall had a negative effect on most of grain quality parameters except crude protein concentration.

The quality of wheat-based food. products, especially bread quality, is significantly affected by the characteristics of the wheat flour, both in term of processing quality and nutritional value. White flour, by far the most used flour in breadmaking, derives from grinding of the grain starchy endosperm. Several studies have demonstrated that the endosperm tissue shows significant inhomogeneity in its chemical composition, with both quantitative and qualitative patterns of tissue distribution observed for all its main storage components. This project has focused on a detailed study of the spatial distributions of proteins and starch within the wheat endosperm, how they are influenced by genetic and environmental factors and how they affect the processing properties of the flour. Multiple technologies, including protein/starch chemistry, immunocytochemistry and microscopy, have been used to achieve the research aims. The results show a clear deceasing gradient in total protein in the endosperm from the subaleurone toward the centre of the grain. Strong spatial gradients were also observed in the composition of gluten proteins. These patterns were best visualised in vivo by Immunofluorescence microscopy. The SE-HPLC profiles, which can be used to predict processing quality, also showed gradients across the grain. The pattern of distribution of starch showed an opposite trend to that of proteins, being higher in the central endosperm cells than in subaleurone cells. 1 The amylose/amylopectin ratio also varied spatially in grain of some of the cultivars. Strong genotype effects were found for all parameters that were measured. Nitrogen fertilisation was found to have a strong impact on the amount of protein (both quantity and quality) and their distributions. Moreover, it also influenced, albeit to a much smaller extent, the amount of starch. The detailed information on protein and starch distribution within endosperm and effects of genotype and nitrogen fertiliser from this study provided knowledge that would lead to greater understanding of protein and starch synthesis as well as nutrition transport within grain. It is also potentially beneficial for improving milling technology and selecting breeding candidates for different purposes.