PHENOTYPIC AND MOLECULAR DIFFERENTIATION OF PECTOBACTERIUM AND DICKEYA SPP. CAUSING POTATO TUBER AND STEM ROT IN NORTH-WESTERN PROVINCES OF IRAN.

Iran is one of the most important potato-producing countries in Asia and Oceania. Approximately 20 percent of potato cultivation in Iran occurs in the North-western provinces. Pectobacterium and Dickeya species cause important diseases in potato crop. They may incite blackleg and are responsible for tuber soft rot in storage, thereby reducing yield and quality. In order to identify and differentiate the species of soft rot bacteria, potato stems and tubers showing soft rot symptoms were collected from potato fields in North-western Iran. A total of fifty strains belonging to Pectobacterium and Dickeya species were isolated and identified from the infected tissues. Phenotypic characterization revealed a considerable variation among strains thus dividing them into five separate groups. Group 1 strains belonged to Dickeya chrysanthemi that were different from the type strain in malonate utilization. Group 2 strains were similar to Pectobacterium betavascularum but were different from the type strain in utilization of raffinose, citrate and D-sorbitol. Group 3 strains showed more resemblance to P. wasabiae but were different from the type strain with respect to acetoin production. Group 4 strains belonged to P. carotovorum subsp. carotovorum (Pcc) and group 5 strains were identified as intersubspecific of Pcc and P. carotovorum subsp. odoriferum. Polymerase chain reaction using pelY primers identified strains belonging to Pectobacterium species but not P. betavascularum.