Infection data and spore counts for cross inoculation experiments

Determining the processes that drive the evolution of pathogen host range
can inform our understanding of disease dynamics and the potential for
host-shifts. In natural populations, patterns of host range could be
driven by genetically based differences in pathogen infectivity or
ecological differences in host availability. In northwestern Italy, four
reproductively isolated lineages of the fungal plant-pathogen Microbotryum
have been shown to co-occur on several species in the genus Dianthus. We
carried out cross-inoculation experiments to determine whether patterns of
realized host range in these four lineages were driven by differences in
infectivity and to test whether there was evidence of a trade-off between
host range and within-host reproduction. We found strong concordance
between field patterns of host range and pathogen infectivity on different
Dianthus species using experimental inoculation, indicating that infection
ability is a major driving force of host range. However, we found no
evidence of a trade-off between the ability to infect a wider range of
host species and spore production on a shared host.