Molecular genetics of resistance to leaf rust (Puccina hordei) in barley (Hordeum vulgare)

Abstract

Barley is a key cereal crop produced globally for animal feed, malt production and direct human consumption. For the Australian agricultural sector, barley is second only to wheat in terms of cereal production. Disease burden is a primary component of yield loss for cereal crops. Cereal crops underpin the global diet thus reductions in cereal yields have a major impact on global food availability and hence food security. Puccinia hordei, the causal agent of barley leaf rust (BLR), poses a significant threat to barley production in Australia and around the globe. P. hordei is a biotrophic fungal pathogen that can result in yield losses of over 60% under epidemic conditions. Disease burden can be addressed economically and sustainably through the use of genetic resistance. This thesis aims to improve our understanding of the genetic components underpinning resistance to BLR and refine methodologies available to assess resistance to BLR in germplasm. A detailed review of the literature is contained in Chapter One. The materials and methods utilized over the course of this thesis are detailed in Chapter Two. Chapter Three details the fine mapping of the BLR resistance locus Rph5 and the generation and characterization of sodium azide mutants with induced susceptibility at the Rph5 locus. Chapter Four investigates allelism and race-specificity among putative Rph2 donor lines and was published in Phytopathology, 110(5):1067-1073. The identification of a race-specific rust resistance gene designated Rph27 is outlined. Chapter Five outlines a novel methodology in barley for assessing adult plant resistance (APR) to BLR and was published in Plant Breeding, 138: 51– 61. Chapter Six provides a conclusion based on the overall findings of the thesis in the context of the field including future directions and perspectives.