Abstract:Common bacterial blight, caused by Xanthomonas axonopodis pv. phaseoli and Xanthomonas fuscans subsp. fuscans, is one of the major constraints to common bean production and causes heavy yield losses and reduces the commercial value of seeds. Contaminated seeds are the primary mean of disease dissemination. This study aimed to detect the pathogens of common bacterial blight on seeds of 60 common bean samples collected from five main production regions. The pathogen colonies of common bacterial blight were isolated from seed extracts of 36 samples on MT medium by dilution-plating method, and the bacteria populations were from 2.49×102 to 5.20×107 CFU per seed. The 36 representative strains were pathogenic on bean cultivar “Yingguohong” by stem inoculation. Based on PCR detection with specific primer pairs, 20 isolates were identified as X. fuscans subsp. fuscans, while 16 were identified as X. axonopodis pv. phaseoli. The results of seed detection showed that common bean seeds used in commerce and research had been contaminated with pathogens of common bacterial blight, it suggests that it is necessary to establish pathogen-free seeds production base and strengthen seed regulation.