Data from: Host specialisation and disparate evolution of Pyrenophora teres f. teres on barley and barley grass

Background Pathogens evolve in an arms race, frequently evolving virulence
that defeats resistance genes in their hosts. Infection of multiple hosts
may accelerate this virulence evolution. Theory predicts that host
diversity affects pathogen diversity, with more diverse hosts expected to
harbour more diverse pathogens that reproduce sexually. We tested this
hypothesis by comparing the microsatellite (SSR) genetic diversity of the
barley leaf pathogen Pyrenophora teres f. teres (Ptt) from barley
(monoculture) and barley grass (outbreeding). We also aim to investigate
host specificity and attempt to track virulence on two barley cultivars,
Maritime and Keel. Results Genetic diversity in barley Ptt populations was
higher than in populations from barley grass. Barley Ptt populations also
had higher linkage disequilibrium levels, indicating less frequent sexual
reproduction, consistent with the Red Queen hypothesis theory that
genetically diverse hosts should select for higher levels of sexual
reproduction of the pathogen. SSR analyses indicate that host-associated
Ptt populations do not share genotypes and have independent evolutionary
histories. Pathogenicity studies showed host specificity as
host-associated Ptt isolates could not cross-infect hosts. Minimum
spanning network analyses indicated two major clusters of barley Ptt. One
cluster represents Maritime virulent and isolates from Western Australia
(WA). Low PhiPt population differentiation between WA populations and
those from Maritime and Keel, indicated a WA origin of the Maritime and
Keel virulences. The main minimum spanning network cluster is represented
by a panmictic population structure, represented by isolates from all over
Australia. Conclusions Although barley Ptt populations are more diverse
than barley grass Ptt populations, this may be a result of the size and
number of founder Ptt populations to Australia, with larger and more
barley Ptt populations introduced. More frequent sexual reproduction of
Ptt on barley grass support the Red Queen Hypothesis and suggest
evolutionary potential of pathogens on diverse hosts are high. Extensive
gene flow of Ptt between regions in Australia is suggested to maintain a
panmictic population structure, with human-mediated dispersal aiding in
virulence evolution of Ptt on barley.