THE NEW PLASMID pEI70 IS PRESENT IN ERWINIA AMYLOVORA EUROPEAN STRAINS

The search for wild type strains of Erwinia amylovora that do not harbor the plasmid pEA29, has led to the finding of more strains of this pathogen carrying a plasmid of about 70 kb recently described and called pEI70. These strains have been found in collections from countries all over Europe and new screenings are under way with strains from other continents. In our survey, the pEI70 has so far been found in E. amylovora strains from 10 European countries: Spain, Ireland, United Kingdom, Slovenia, France, Italy, Poland, Belgium, Czech Republic and the Netherlands. The numbers of strains carrying this plasmid varied from almost every strain analyzed (e.g., in Belgium) to only a few in other countries. A multiplex PCR protocol has been devised to check for the presence of pEA29 and pEI70 in a single assay. Restriction analyses and hybridizations demonstrated that this large plasmid was similar in all the strains analyzed. Stability after 200-generation serial transfer experiment showed 100% maintenance even in the absence of pEA29. Virulence assays on pear flowers showed no differences between some of these strains and reference E. amylovora strains. The cloning and sequencing of pEI70 is under way to analyze the gene content and perform comparison analyses and identification of putative ORFs, trying to predict its possible role.