Kehoe, StephenStephenKehoe2022-12-072022-12-072022 the A2022http://hdl.handle.net/10197/13290Pressures on the global food supply are increasing due to an increased population and climate change. A more productive and efficient way of supplying food is needed. The green revolution of the 1960’s gave significant increase of food production and its efficiency. Now a second green revolution is needed to meet global demands and in the case of cereal crops it is thought this will come from crop roots. Roots are considered to be half of a plant, yet the number of studies on this hidden half is far less than that of the shoot. One of the main reasons for this is the difficulty is phenotyping roots in their natural environment without growing them under artificial conditions. Techniques such as shovelomics have recently been developed for use on wheat in the field. The advancement of technology is also aiding the phenotyping of roots with techniques such as X-ray Computed Tomography (CT) now available that can phenotype roots non-destructively in 3-dimentions (3D). With these new methods available, this project aimed to phenotype the roots of commercial cereal cultivars to identify differences in the roots using field and pot-based trials so that any beneficial phenotypes can be included in breeding programs. To address a general lack of root phenotypic information for cereal crops, this work collected and compared root phenotypes of modern cultivars of oats, barley and wheat. From this the barley cultivars demonstrated a trend for more soil exploration and thus better access to nutrients. There is a gap in the root phenotypic information of oats and two years field trials were completed to evaluate and compare three cultivars of winter sown oats. These trials demonstrated a link between the developmental stage of above and below ground plant parts at the tillering and flowering stages of growth. Both the field trials and seedling trials established a set of phenotypes against which future work can be compared. Roots are the frontline when it comes to waterlogging or nitrogen stresses. In the future, waterlogging stress is set to worsen and become more frequent due to climate change. One of the effects waterlogging has on soil is to form hypoxic conditions and one way that plants such as barley reduce this stress is through the formation of aerenchyma. Current methods for visualising aerenchyma formation in roots are mostly 2-dimensional (2D) and involves processes to embed roots in a resin for microscopy sectioning. This body of work developed an aerenchyma spatio-temporal identification and quantification method in 2D and 3D using X-ray CT with an image analysis pipeline. This new method can identify aerenchyma as early as 9-days post waterlogging and has the potential to support the selection of breeding markers. Nitrogen fertiliser application causes an increase in the yield of cereals. However, its costs are rising and if used in excess it can have detrimental effects on the environment. Roots are the main interface for nitrogen uptake and yet little is known about the effect different rates of nitrogen has on roots, especially for oats. This work revealed that from 0 to 80 kg ha-1 of nitrogen, shoot growth increased but above 80 kg ha-1 branch class data demonstrated an increase of the thickest (width) roots and as the rate of nitrogen increased further a difference was seen in the thinner root classes. An increase of roots at higher rates results in more soil explored which in turn gives higher nutrient availability to the plant. This work investigated roots of cereals under a range of different soil environments to provide a comprehensive data set of root information and pushes the boundaries of scientific knowledge on roots. This enables further research to be conducted on roots with the aim of improving future cultivars to be more nutrient efficient and better able to tolerate abiotic stresses. This would be done through the identification of genetic marks for root traits to be used in breeding programmes.enRootsPhenotypingWaterloggingNitrogenDoctoral Thesis2022-11-29https://creativecommons.org/licenses/by-nc-nd/3.0/ie/