DESCRIPTION OF ERWINIA PIRIFLORINIGRANS SP. NOV., CAUSAL AGENT OF PEAR BLOSSOM NECROSIS

Erwinia sp. strains were isolated from necrotic pear blossoms in Valencia, Spain and they were pathogenic on pear flowers. A selection of isolates was compared to reference strains of E. amylovora and E. pyrifoliae and to other species of Enterobacteriaceae by a polyphasic approach. The results of phenotypic analyses showed that they constitute a homogeneous phenotypic group different from other Erwinia species. The PCR products obtained with different primers and the plasmid content followed by restriction analysis showed differences, but also several similarities, when compared to E. amylovora and E. pyrifoliae reference strains. Phylogenetic analysis of 16S rDNA sequences showed that they could not be robustly grouped with any single known species. Furthermore, the strains from necrotic pear blossoms constituted a single DNA hybridization group which was 87 to 100% related to the strain from necrotic pear blossoms used and less than 50% to E. amylovora and E. pyrifoliae strains. Consequently, the isolates from necrotic pear blossoms are proposed as members of a new species for which the name Erwinia piriflorinigrans is proposed.