Fig. 5

Recombination analysis between P. syringae strains from different phylogroups (PGs). Pairwise phylogroup recombination events were normalized based on the pan-genome size, the number of strains, and the total branch length for each phylogroups pair. a Regression analysis of recombination rates and corresponding non-synonymous substitution rates (Ka). There is a significant negative log linear relationship between recombination rates and Ka for strains within the same phylogroup and between different primary phylogroups (F = 49.51, df = 30, p < 0.0001, r² = 0.6227); however, the inverse relationship exists when comparing more distantly related strains from different secondary phylogroups and strains from primary and secondary phylogroups (F = 10.58, df = 32, p = 0.0027, r² = 0.2485) b Regression analysis of recombination rates and corresponding synonymous substitution rates (Ks). The same significant negative (F = 54.53, df = 30, p < 0.0001, r² = 0.6451) and positive (F = 11.40, df = 32, p = 0.0019, r² = 0.2627) log linear relationships were observed for strains within the same phylogroup and between different primary phylogroups, and more distantly related strains from different secondary phylogroups and strains from primary and secondary phylogroups, respectively c Hierarchical clustering of homologous recombination frequency between phylogroups of the P. syringae species complex. Pairwise distances between phylogroups were calculated using the Jaccard coefficient method, based on the normalized pairwise recombination rates. Note that phylogroup 10 (PG10) is a primary phylogroup that is more closely related to phylogroups 1, 2, 3, 4, 5, and 6. Agricultural vs. Environmental labeling indicates that the bulk of the strains in these phylogroups come from these sources