This was achieved by comparative genomics of X. arboricola strains differing on their pathogenicity, including the nonpathogenic X. arboricola strains isolated from walnut and evaluated in this study (CFBP 7634 and CFBP 7651), and X. arboricola strains (CFBP 14, CFBP 44, and CFBP 124) isolated from Prunus. Regardless of the contributions of these comparative genomics studies in highlighting the importance of T3SS and T3E genes, dedicated functional studies are still required to identify essential genes for successful infection. This evidence concerns the gene MVB12A and infection.