Abstract:Celery bacterial soft rot has become severe in Beijing, especially in Shunyi and Tongzhou district. In order to identify the causal agent of the disease, bacterial strains were isolated from the diseased celery stems, and the pathogenicity of the isolates was then confirmed by inoculation of these isolates on celery seedling following Koch's postulation. Fifty-four pathogenic isolates were obtained. Based on morphological observation, physiological, biochemical and Biolog test, as well as multilocus sequence analysis of six concatenated housekeeping gene sequences(pgi、rpoS、mdh、proA、mtlD、icdA), the causal pathogen was identified as Pectobacterium carotovorum. Among these disease-causing isolates, 45 strains were identified as P. carotovorum subsp. odoriferum with a frequency of 83.33%,6 strains as P. carotovorum subsp. carotovorum with a frequency of 11.11%, and 3 strains as P. carotovorum subsp. brasiliensis with a frequency of 5.56%. These results indicate that the causing agents of celery bacterial soft rot in Beijing were identified as three subspecies of P. carotovorum, and P. carotovorum subsp. odoriferum was dominant.