The phenotypic and genotypic characteristics of causal agents of potato bacterial soft rot in Ardabil province of Iran

Bacterial soft rot causes severe damage to potatoes and is responsible for considerable economic losses in potato crop during both growing season and storage period. The most common causal agent of potato soft rot worldwide is Pectobacterium carotovorum (Pc); however in Iran, two other species: P. atrosepticum and P. wasabiae have been reported. Identification and assessment of genetic variation in pathogen populations are very important to understanding taxonomy, epidemiology, and management of a pathogen. In this study, potato stems and tubers showing soft rot symptoms along with their surrounding soil were collected from fields and seed storages of Ardabil province. A total of 33 pectolytic bacterial strains were isolated on nutrient agar and eosin methylene blue culture media. The isolated strains and five standard strains belonging to P. atrosepticum, P. carotovorum and Dickeya dianthicola were studied. The strains were identified as P. carotovorum subsp. carotovorum on the basis of phenotypic characteristics including: gram-negative, facultative anaerobic, soft rot production on potato slices, growth at 37 °C, and inability to produce acid from α-methyl-D-glucoside and also molecular identification using species-specific primers. Based on Y1/Y2 and ExpccF/ExpccR primers, the expected amplicons (434 and 550 bp fragments, respectively) were obtained for all strains and the standard strains belonging to P. carotovorum. According to rep-PCR and cluster analysis using UPGMA and NTSYS 2.1 software, the selected strains were categorized into two main groups and four subgroups. Rep-PCR indicated different levels of genetic heterogeneity among Pcc strains, however, no clear correlation was found between clustering and the geographical origin of the strains.

The phenotypic and genotypic characteristics of causal agents of potato bacterial soft rot in Ardabil province of Iran Keywords:

Pectobacterium carotovorum , rep-PCR , species-specific primers