Occurrence of Pectobacterium wasabiae in potato field samples

During the growing seasons of 1996 and 1997, samples of potato stems and tubers with symptoms of blackleg and soft rot were collected in different regions in Poland. After growing to pure cultures on crystal violet pectate (CVP) medium, isolates of bacteria were identified as Pectobacterium spp. on the basis of their ability to degrade pectate and with the use of biochemical tests. About 43 % strains isolated from 122 different plant samples were identified as Pectobacterium carotovorum subsp. carotovorum, whereas the rest of the pectinolytic bacteria was identified as Pectobacterium atrosepticum. A recent screening of these isolates with recA PCR-RFLP allowed identification of 18 different RFLP groups within the tested P. c. subsp. carotovorum strains. The third largest group of the tested P. c. subsp. carotovorum strains (14 %), which were assigned to the profile 3 recA PCR-RFLP, was re-identified as Pectobacterium wasabiae (formerly Erwinia carotovora subsp. wasabiae) on the basis of recA and 16S rRNA genes sequences. About 50 % of P. wasabiae isolated from potato, in contrast to horseradish isolates of P. wasabiae, have an ability to grow at 37A degrees C and some of them grow on media containing 5 % of NaCl. In a pathogenicity test with 11 strains of P. wasabiae these strains showed a high capacity to rot potato tubers.