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Common bacterial blight caused by Xanthomonas campestris pv. phaseoli is an economically important disease in beans Phaseolus vulgaris. In this research Xcp characteristics, interactions with other seedborne bacteria and host resistance were studied. Xcp was isolated from fresh leaves and pods collected in Puerto Rico and dried leaves from Central America. Plasmid DNA from 20 Xcp strains was extracted and digested with Bcl I, Csp 45 I, EcoICR I, Hae II, Hae III and Hinf I restriction enzymes. Plasmids were detected in all 20 Xcp strains, being Bcl I, Eco ICR I useful to distinguish eight groups. Seedborne bacteria isolated were: Pantoea agglomerans, Xanthomonas campestris, Enterobacter agglomerans, Sphingomonas paucimobilis, Pseudomonas fluorescens and Flavimonas oryzihabitans. P fluorescens, S. paucimobilis, F. oryzihabitans and E. agglomerans were Xcp inhibitors. Differences in virulence Xcp and confirmation of the occurrence of physiological races were found. Genomic DNA was extracted to identify bean genotypes with resistance to Xcp using the SCAR molecular markers: SAP 6, SU 91, BC 420 and R 7313. Lines XAN 159, VAX 6, HR 45, OAC 88-1, ICB-3 and PR9443-4 were resistant. SCARs SAP 6 and SU 91 classified the highest number of resistant genotypes.