Investigating Irish heritage barley responses to waterlogging

Understanding how our agricultural production systems will respond to the changing climate is fundamental to our ability to safeguard food security. Waterlogging occurs when the soil becomes saturated and the roots of the crop are inundated by water. Waterlogging stress is a yield reducing stress that is expected to become more prominent in the near future. Barley (Hordeum vulgare. L), Irelands most produced cereal crop, is particularly sensitive to waterlogging stress. It has been suggested that modern barley varieties are more susceptible to stress than heritage lines due to their genetic bottleneck. In this work, I examine the waterlogging tolerance of a collection of nine Irish heritage two-row spring barley lines in comparison to five commercial lines in both field and glasshouse conditions. Working with the hypothesis that heritage barley lines may be more tolerant to waterlogging stress, I sought to investigate the responses of these lines to waterlogging using image-based phenotyping. In chapter one, the heritage collection selected for this work and associated history is introduced. In the second chapter, a literature review of the of the use of phenotyping methodologies to assess waterlogging tolerance across various crops is presented to inform experimental design of the subsequent work. Chapter three details the optimisation of a protocol to screen for waterlogging tolerance in glasshouse conditions using image-based phenotyping. In chapter four, the previously optimised protocol is used to screen the collection of nine heritage and five commercial lines using RGB and hyperspectral sensors. The fifth chapter discusses field trials conducted from 2020-2022 at UCD Lyons Research Farm. The barley lines in this thesis were included in screening of a larger collection of northern European barley lines. Though field data was subject to high inter annual variability, two lines ranked highly in both glasshouse and field screenings ‘Irish Goldthorpe’ and ‘Old Irish’. Taken together, this thesis explores the waterlogging stress responses of a collection of Irish heritage barley through image-based phenotyping and harvest parameters under both field and glasshouse conditions. The stress performance of the heritage collection relative to the controls support the thesis hypothesis that heritage germplasm should be explored as a viable genetic source for waterlogging tolerance. Altogether, this work paves the way to an improved understanding of barley physiology under waterlogging stress and reinforces the importance of genetic resources contained in germplasm banks.