We study the population structure of R. commune in homogeneous and heterogeneous host populations to determine the effects on the evolution and dynamics of the pathogen. The interaction between host and pathogen populations occurs in two ways: the infection of the plant by the fungus – epidemiological, and the selective pressure exerted by various spatial arrangements of host genotypes on the pathogen population – evolutionary. The dynamics of these processes are complex and closely interdependent. In an agricultural setting, the problem is simplified by the fact that the co-evolution of the host population need not be considered.

Figure: Pathogenicity, origin and SSR genotype of Rhynchosporium commune isolates

The mechanistic basis whereby mixtures reduce disease through deployment of trait diversity, that is, the epidemiological parameters, are investigated both experimentally and through modelling.

In the field we have investigated what arrangements of hosts of varying susceptibility most affect the spread of the disease. We have utilised morphological variants and different resistance types, as determined by QTL mapping and linked markers, in barley doubled-haploid lines. These are deployed in different proportions and geometric patterns to manipulate the host epidemiological and selection pressures.