Pectobacterium carotovorum subsp. brasiliense and Pectobacterium carotovorum subsp. carotovorum as causal agents of potato soft rot in Algeria

During surveys carried out in 2014 and 2015 in Algerian potato fields, severe bacterial tuber soft rot was observed. Twenty-one Gram-negative pectinolytic bacterial isolates were obtained from diseased potato tubers. These induced a hypersensitive reaction and soft rot symptoms when inoculated in tobacco leaves and potato tubers, respectively. PCR amplification using the Y1/Y2 primers demonstrated that all of the bacterial isolates belonged to the genus Pectobacterium. Phylogenetic analysis using partial malate dehydrogenase (mdh) gene sequences revealed that six and 15 isolates grouped with Pectobacterium carotovorum subsp. brasiliense and Pectobacterium carotovorum subsp. carotovorum reference strains, respectively. Multilocus sequence analysis of concatenated partial sequences of the acnA, atpD, gyrB and infB genes carried out on selected bacterial isolates confirmed the results obtained with the mdh gene sequences. PCR amplification with the BR1f/L1r primers that are specific for P. carotovorum subsp. brasiliense confirmed that six of the Algerian isolates belonged to this taxon.