Genetic Diversity of Xanthomonas arboricola pv. fragariae Strains and Comparison with some other X. arboricola Pathovars using Repetitive PCR Genomic Fingerprinting

The genetic relationship within 26 Xanthomonas arboricola pv. fragariae strains and between this pathovar and 20 strains of X. arboricola pv. corylina, 22 strains of X. arboricola pv. juglandis and 16 strains of X. arboricola pv. pruni has been assessed bymeans of repetitive polymerase chain reaction (rep-PCR) using Enterobacterial Repetitive Intergenic Consensus), BOX (BOXA subunit of the BOX element of Streptococcus pneumoniae) and repetitive extragenic palindromic primer sets. Cluster analysis was performed by means of unweighted paired group method using arithmetic average (UPGMA). Upon rep-PCR and UPGMA cluster analysis, a relevant genetic diversitywas found within the strains. The overall similarity, however, was high (i.e. 80%). The four X. arboricola pathovars showed similar but clearlydifferent genomic patterns and clustered into four different groups, with X. arboricola pv. corylina and X. arboricola pv. juglandis more closelyrelated to X. arboricola pv. fragariae. Representative strains of X. arboricola pv. fragariae and the putative xanthomonads isolated from strawberryleaves showing leaf blight symptoms underwent pathogenicity tests. After artificial inoculation, X. arboricola pv. fragariae induced necrotic spots accompanied, sometimes, bya chlorotic halo. The blackening of the leaf veins and peduncle was, sometimes, also observed. The four putative xanthomonads isolated from diseased strawberryleaves and not inducing symptoms after artificial inoculation, clustered apart from X. arboricola pathovars