Production and consumption of ruminant products is partly being held accountable for the increasing global challenges of human health and climate change. Also, increasing demand for food, feed and fuel is placing growing pressure on land availability. One area under investigation in response to these challenges is fatty acid content of forages. This thesis sets out to investigate the variation and relationships between fatty acids, lipids, chlorophyll and other nutritional aspects of perennial ryegrass. Additionally, it will investigate alternative methods to predict fatty acids in forage. The core experiment involved twenty-four genotypes from two perennial ryegrass populations. Fatty acids were found to increase in leaf material during a growing season. Genotype differences in fatty acid content and composition were found which were broadly consistent across the growing season. Fatty acids correlated positively with crude protein but negatively with water-soluble carbohydrates. A positive and consistent relationship was found between chlorophyll and fatty acids across the growing season. The use of a chlorophyll meter to estimate fatty acid content did not perform very well, due to poor relationships with in vitro chlorophyll, however near-infrared reflectance and Fourier-transform mid-infrared spectroscopy had acceptable prediction accuracies for use as a screening tool. The accuracies of these prediction methods could be improved with further development using larger datasets. Investigation of the lipid composition revealed that galactolipid proportion was the main contributor to increased total fatty acid content in the high FA genotypes. While phospholipid proportion was minimally affected and neutral lipid negatively affected by increased total fatty acid content. Further work is needed to determine the underlying genetic control of fatty acid and lipid synthesis in perennial ryegrass. Additionally, a great deal more research is needed to establish environmental and genetic effects on lipid composition of forages.

Grasses from the genus Miscanthus are among the most promising dedicated lignocellulosic energy crops. Despite their potential, cell wall recalcitrance to deconstruction still hinders widespread use of its biomass as a bioenergy and biomaterial feedstock. Consequently, the advancement of our knowledge concerning the roots of recalcitrance is a pressing matter. To clarify chemical, structural and biological features underpinning recalcitrance in miscanthus cell walls, here are presented the results of an in-depth cell wall analysis following a multidimensional approach, considering: different developmental stages, stem vs. leaf compositional variability and various genotypes. Early results showed inverse correlations between lignin content and ethanol production in stem tissues but not in leaves. FTIR spectroscopy showed that tissue and development-derived compositional differences are mostly associated to structural carbohydrates. Accordingly, subsequent research was shifted to focus on the composition of polysaccharide fractions of the cell wall and on the exploration of structural associations. Glycome profiling allied to glycan immunolocalisation studies further elucidated the nature of compositional variation and provided detailed information about in situ distribution of selected carbohydrate epitopes. Key observations demonstrated that stem and leaf biomass is differently modified throughout development, leading to harvest and tissue-specific features at the level of glycan abundance, distribution, composition and ornamentation. These differences have substantial effects on the amenability to deconstruction; however, the results highlighted the limited predictive power of single traits as indicators of cell wall recalcitrance. Instead, a holistic view of the cell wall is promoted, which considers that different components have variable impacts on recalcitrance depending on overall cell wall assembly. These outcomes effectively emphasised the value of the results-driven approach followed in this thesis. Ultimately, the constructed detailed portrait of the cell wall will help steer breeding and engineering strategies for the development of superior energy crops and help advance biorefining strategies. Key words: Miscanthus, biofuel, plant cell wall, FTIR, lignin, carbohydrate, glycan, glycome profiling, immunolabelling, antibody, recalcitrance, lignocellulose, biomass.

Brachypodium, as a sister to the core pooids containing wheat, barley, oats and rye, represents a good model and point of comparison for the study of development and evolution in temperate cereals. Using a comparative cellular developmental and transcriptomic approach, we investigated regulation of key stages in grain development. This was achieved by generating a transcriptome incorporating several distinct developmental stages of Brachypodium grains; pre-anthesis ovaries, young grain (1-3 DAA), mid-length grain (3-8 DAA), full-length (8-15 DAA) and mature grain (15-24 DAA), mature grain (without embryo), germinating grains and seedlings stage. By looking at the differential expression of genes through grain development we identified clusters that coincide with the initiation of key developmental stages, such as the initiation of endosperm proliferation, cellularisation and differentiation, as well as the activation of specific metabolic pathways, such as starch and protein biosynthesis. Focus was given to members of the YABBY gene family that have an established role in promoting abaxial cell fate and as master regulators of reproductive development in eudicots, but with less clarity in grass species. Using Brachypodium as the model plant for cereal crops, the orthologues of YABBY genes in grasses were identified and subjected to detailed phylogenetic, expression and functional analyses using Bayesian Interference (BI) analyses, RT-PCR, transcriptomics, mRNA in situ hybridization (ISH) and RNAi. Based on several analyses, YABBY6 was suggested as a novel candidate of transcription factors regulating seed development in Brachypodium. Metadata from Chapter 2 were used to extract similar expression genes of YABBY family members and potential motifs regulated in polarity networks involving YABBY genes were suggested.

Tulipa (Tulips; Liliaceae) is a genus of horticulturally important flowering bulbs (geophytes) comprising approximately 76 species. The taxonomy of the genus has long been confused. The most recent revision of supra-specific taxa has used DNA sequence data to inform taxonomy for the first time. This study sampled 25 species, so there is scope for better sampling to increase understanding of the evolutionary history of the genus and to contribute to a more robust taxonomy. The current study sampled 74 plants representing 61 species. Two nuclear gene regions were used for phylogeny reconstruction, and for both regions a complete survey of the extent of intra­individual polymorphism was made. The study using the first region, the internal transcribed spacer (ITS), included 347 sequences in total. Phylogeny was reconstructed using Bayesian and Maximum Likelihood and network methods. Significant intra-individual polymorphism was revealed, with only 18 species with all clones comprising a monophyletic group. One of the four subgenera were monophyletic, but core subgenera were recovered. Similarly, well-supported clades corresponded to the core species of several sections, though none was monophyletic. A second nuclear gene region was identified for phylogeny reconstruction by scrutinising published EST data from T. gesneriana. The nuclear gene region was a candidate single copy nuclear region (conserved orthologous sequence; COS). The final alignment included 240 sequences and the same plants as the ITS study. As for the ITS region, significant intra-individual polymorphism was revealed, and existing supra-specific taxa were not monophyletic. The extent of intra-individual polymorphism precluded concatenation of the two alignments for total evidence analysis. However, inspecting trees for common patterns revealed some core groupings. Subgenus Tulipa does not appear to be monophyletic, as has been previously proposed. Several sections could be re-circumscribed. In this study we do not make taxonomic changes, because the study highlights problems with using few or single plants to represent species, especially when the plants are not wild collected. A detailed study of wild-collected Tulipa kurdica included phylogenetic and morphometric analyses. Plants in trade as T. kurdica do not correspond to the wild-collected plants or to plants used in previous phylogenetic studies to represent T. kurdica, though these studies have been used to justify placing T. kurdica in synonymy with T. humilis. T. kurdica may be more closely related to T. pulchelta than to T. humilis.

No description available.

This study has (a) evaluated the biodiversity in toxigenic mycobiota associated with maize from subsistence farmers’ stores in five climatic regions of Lesotho in two seasons, (b) compared the effect of ecophysiological factors on interactions between atoxigenic (AFL-) and toxigenic (AFL+) Aspergillus strains and control of aflatoxin B1 (AFB1) contamination of maize, (c) examined the mechanism of action of AFL- strains in relation to mycelial growth rate, sporulation, germination rate, germ tube extension, C-source utilisation patterns and hydrolytic enzymes and (d) examined ecophysiological approaches to enhance competitiveness of the atoxigenic strains.

2,3,5-triiodobenzoio acid (TIBA) modifies the normal pattern of vascular tissue in fronds of Lemna minor. This effect has been investigated in an attempt to analyse the factors controlling the pattern which normally develops. Experiments carried out to this end have been as follows. (1) TIBA was added to the culture solution in a range of concentrations and the pattern of vascular tissue of fronds growing in this solution investigated. (2) the effect of added auxins on the response of Lemna to TIBA was investigated. (3) Determinations were made of the effect of TIBA on the balance of growth regulators in the frond by means of paper partition chromatography and Avena coleoptile cylinder assay. (4) The uptake and metabolism of TIBA by the frond was studied using radioaotive TIEA. (5) Tests were made of the effect of other di- and tri-halogen substituted benzoic acids on the vascular system of L. minor.

Within the horticultural industry, clonal propagation is desirable allowing for the maintenance of true lines, with more uniform cropping and flowering characteristics. Clonal propagation through tissue culture can be expensive, requiring equipment and facilities not always available to the breeder, whilst more traditional methods of clonal propagation may be slow, producing limited numbers. Many Alliums produce bulbils or have the ability to produce bulbils if appropriate conditions prevail. Allium ampeloprasum var. babingtonii always produces both sterile florets and bulbils in the inflorescence as well as daughter bulbs and bulblets. The ability to manipulate the inflorescence towards the production of bulbils may lead to improved methods of clonal propagation. Literature suggests that bulbil production may involve reversion or partial reversion of floral primordia at critical stages in inflorescence development. Wax embedding, sectioning and staining techniques have been used to examine bulb physiology, and allowed the construction of a developmental timetable. A protocol was developed for the maintenance of apices in tissue culture to monitor floral determination of the apex. The sampled population of Allium ampeloprasum L. var. babingtonii (Borrer) Syme was found to have both a vernalization requirement and a maturity requirement for floral competence. Vernalization for six weeks at 7 C produced 100 % flowering in plants with a minimum size of 3 cm diameter or approximately 13 g mass at the beginning of the growth season, producing ten or eleven leaves prior to expression of the floral state. Determination occurred during February the meristem widened followed by elongation of the scape and development of the spathe. Cymes develop in a regular pattern over the inflorescence, florets forming initially with bulbils developing at the base of the pedicels. Gene expression in Allium species has been not recorded in detail, but comparisons with Arabidopsis and other monocotyledons such as rice (Oryza sativa) have provided a working model. Degenerate primers were constructed based on the rice RLF (Rice LEAFY homologue) gene. This was used to establish the presence of a putative homologue in Allium ampeloprasum var. babingtonii (ABLFY), this being expressed in floral meristems but not vegetative meristems

Lolium perenne L. (perennial ryegrass) is the most widely used turf and forage grass grown in temperate climates throughout the world, commonly found on sports grounds, and in cattle and sheep farming systems. The introduction of new cultivars of L. perenne with improved agricultural performance has relied on traditional breeding methods. Nuclear and plastid transformation provides an alternative approach to obtain plants with desired phenotypes, some of which would be difficult to achieve by classical breeding.

No description available.