The effect of the barley pathogen Ramularia collo-cygni on the quality of malt and the potential to control the disease through host resistance

Across the cereals sector, there is much interest in grain health and the presence of seed borne pathogens, especially in barley for malting. One of the major economic barley diseases in Scotland is Ramularia leaf spot (RLS), caused by the dothidiomycete fungus, Ramularia collo-cygni . This fungus has been shown to reduce grain yield and quality. It also has a seed borne stage in its life cycle. This BARIToNE PhD project builds on previous research by investigating (1) the effect of R. collo-cygni presence in harvested grain on malting and sprit (2) utilising previous genome wide analysis, which identified candidate gene regions associated with field resistance, we will genetically dissect this region using multi-parent populations developed from landraces and an elite cultivar (3) the potential for these crosses to display increased resistance to the pathogen will be validated in controlled condition and field experiments. The project relates strongly to the reduced input theme as RLS control relies on fungicide sprays just before head emergence. To address these three objectives, the project will combine biochemistry, genetics, genomics and field phenotyping in the following experimental approaches:



Biochemical approaches. Micromalting of infected samples to determine malt quality (predicted spirit yield), diastatic power and wort viscosity in grain samples with varying levels of Rcc (including some lines with enhanced tolerance/resistance) . Then alcohol yield, congener profile and flavour profile of spirit produced from that malt. This will provide robust evidence on the impact of the fungus on product quality and also the impact of breeding for resistance on grain quality.



Genetics and genomic approaches. A recent genome wide association analysis has highlighted candidate genes on the barley chromosomes which are associated with disease resistance in field experiments. An analysis will be conducted on a wider panel of genotypes including landrace accessions from a legacy collection, to identify genotypes which carry the candidate genes and develop novel germplasm for validation in controlled and field studies.



Field disease phenotyping and validation approaches. i) Testing predicted resistance. The levels of resistance in the panel of genotypes analysed in part 2 will be tested in controlled conditions and field experiments to determine levels of resistance to symptom expression. ii) Resistant and susceptible lines will be tested for levels of apoplastic leakage and cuticle thickness to determine their potential influence on disease levels.



Throughout the research programme, the student will have opportunity to engage with broader strategic research on crop health and improvement.