Plant pathogens are important forces in shaping the ecology and evolution of host plant populations. However, their impact depends in part on the extent of genetic variation for resistance in the host. In this study, we asked how genetic variation in Midwestern populations of Arabidopsis thaliana affected the un-manipulated growth and diversity of multiple bacterial species. The occurrence and density of three known pathogens (Pseudomonas viridiflava, P. syringae and Xanthomonas campestris) was sampled in six populations, and diversity within each bacterial species was assessed using BOXA fingerprinting. Genetic diversity of A. thaliana hosts was assessed by genotyping 149 single nucleotide polymorphisms distributed across the genome. After monitoring the growth of these three pathogens in A. thaliana leaves, we found that infection rates of all three pathogens vary significantly between host populations, as does the distribution of genetic diversity in Arabidopsis. By examining the frequency, abundance and within species diversity of pathogens isolated from different A. thaliana genotypes, we hope to clarify the importance of host genotype for disease resistance and pathogen virulence in the field.
