Genomic comparison of citrus-associated Xylella fastidiosa (Xf) strains by microarray hybridization showing the distribution of ORFs with reference to the genome of Xf strain 9a5c. Chromosomal ORFs are linearly represented, from ORF Xf 0001 to ORF Xf 2782, followed by ORFs from plasmid pXf 5.1 (from ORF Xf a0001 to Xf a0065). ORFs present in the genome of each tested strain are represented in grey, while missing ORFs are represented in black. ORFs present in greater copy number in the genomes of the tested strains are represented in white [see 26]. The genomic profiles were used to construct a hierarchical grouping of the strains and the robustness of the branching profile was verified by bootstrap analysis, using TMEV (the number next to each branch represents the bootstrap values for 100 permutations). The location of Genomic Islands (GIs) and putative Genomic Islands (pGIs) in the genome of Xf strain 9a5c are also shown [see 26].