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Table 1 Predicted and observed Rhynchosporium commune diversity estimates under the contrasting host diversities and pathogen census population size

From: Weeds, as ancillary hosts, pose disproportionate risk for virulent pathogen transfer to crops

  Barley Barley grass
  Large pathogen pop size Genetically uniform host   Small pathogen population size Genetically diverse host  
R. commune diversity Predicted Predicted Observed Predicted Predicted Observed
Neutral genetic diversity:       
 No. of SSR alleles Many Few Many Few Many Few
Ne Large Small Large Small Large Small
 No. of MLGs Many Few Many Few Many Few
 Mode of reproduction/linkage disequilibrium - More asexual/high linkage disequilibrium More sexual/lower linkage disequilibrium - More sexual/low linkage disequilibrium More asexual/higher linkage disequilibrium
 Migration More from barley to barley grass More from barley grass to barley More from barley grass to barley More from barley to barley grass More from barley grass to barley More from barley grass to barley
Diversity under selection:       
 No. of effector alleles - Few Few - Many Many
 No. of pathotypes - Few Few - Many Many
 Aggressiveness - Less Less - More More
  1. Host dynamics (taken as a given based on literature) for barley is a large acreage/population size with small N e (few cultivars used), inbred monocultures, assumed few resistance genes/alleles and higher disease (R. commune) incidence (large pathogen census population size). Barley grass is a weedy annual which may have a smaller population size than barley (on average less plants), is genetically diverse and thus has a large Ne, outcrossing, assumed to have many resistance genes/alleles and has lower disease (R. commune) incidence (small pathogen census population size). Observed pathogen genetic diversity and effective population sizes are as observed at neutral loci (SSRs) and traits that may be under selection (effector locus Nip1, pathogenicity). Predictions and observations in bold indicate when results confirmed predictions