Molecular typing of Pectobacterium carotovorum isolated from potato tuber soft rot in Morocco

Twenty-two isolates of Pectobacterium carotovorum were collected from soft-rotted potato tubers originating from different production areas in Morocco, and their phenotypic and genetic characteristics were investigated. All of the isolates were identified as P. carotovorum by API 20E (identification kit) system, and yielded a 434-bp DNA fragment of the pectate-lyase-encoding pel gene in PCR experiments. Collected strains were also evaluated for their susceptibility to 11 different antibiotics: Sulfamethoxazole/trimethoprim (SXT), Ceftazidime (CAZ), Ciprofloxacin (CIP), Cefotaxime sodium (CTX), Imipenem (IPM), Gentamicin (CN), Amikacin (AK), Colistin sulphate (CT), Netilmicin (NET), Ampicillin (AMP) and Cephalothin (KF). Of the total P. carotovorum strains isolated, 5 were resistant to only two antibiotics: Ampicillin and Cephalothin. Evaluation of genetic diversity was performed on all isolates by molecular typing with Enterobacterial Repetitive Intergenic Consensus (ERIC-PCR). Results showed the isolates to be distributed on 2 major clusters subdivided into many subclusters. The genetic diversity within the potato strains of P. carotovorum subspecies is shown. No correlation between ERIC-PCR analyses, suscebtibility patterns, geographic areas and year isolated was observed. These results may indicate that the tuber could be the main source of contamination. In conclusion, the ability to distinguish Pectobacterium carotovorum strains from diseased potato with PCR based assay will be useful for strain relatedness studies of this pathogen in Morocco.