Characterization and differentiation of Irish Erwinia amylovora isolates

Between 1986 and 1998, isolates of Erwinia amylovora were obtained from rosaceous plant species throughout Ireland. Sixty five of these isolates have been compared with 10 E. amylovora isolates from Bulgaria, the Czech Republic and Greece, seven other Erwinia isolates and one Pseudomonas isolate (83 isolates in total). Their identity was confirmed by the pear test and by chromosome and plasmid-specific polymerase chain reaction (PCR) analyses. Random amplified polymorphic DNA ( RAPD) analysis was used to study the genetic variability of the 65 Irish isolates. Six random primers (CUGEA 1, 2, 3, 4, 5 and 6) were used for random amplified RAPD analysis; the degree of amplification differed with the primers, but all produced at least 13 ( CUGEA 1) and at most 27 ( CUGEA 5) different RAPD profiles. Phylogenetic analysis of the RAPD profiles showed that 44 of the 65 Irish isolates showed genetic homogenicity (s greater than or equal to 92), but the remaining 21 isolates were more genetically diverse than the other Irish isolates and the foreign E. amylovora isolates. There was no significant relationship between the genetic variability of the Irish E. amylovora isolates (based on RAPD analysis) and the host species, year of isolation or their geographical origin.