Characterization of an Erwinia sp. isolated from necrotic pear blossoms in Valencia, Spain.
A Gram-negative bacterium was consistently isolated from necrotic blossoms of pear cultivars 'Ercolini' and 'Tendral' in Valencia, Spain, in 1999, 2000 and 2001. The symptoms resembled those of fire blight but affected only blossoms and did not progress to other parts of the trees. Isolates showed colony morphology similar to those of Erwinia amylovora on King's B, SNA and CCT media, and their pathological, microbiological and molecular features were studied. The pear isolates were identified as an Erwinia sp. and were able to elicit the hypersensitive reaction in tobacco and necrosis in detached pear flowers, but were unable to develop specific E. amylovora symptoms in immature pear fruits, pear shoots, apple and quince slices, and loquat leaves. They showed an API 20E pattern close to E. amylovora. Dendrograms from API biotype 100 tests showed that the pear isolates and E. amylovora were clustered in different phena. Serological results were similar to those of E. amylovora in IF using polyclonal or monoclonal antibodies but different in ELISA using specific E. amylovora monoclonal antibodies. PCR assays with primers from 23S rDNA sequences of E. amylovora were positive but no signal was obtained with primers from plasmid pEa29 or from chromosomal DNA sequences. Macrorestriction and subsequent PFGE analysis produced patterns different to E. amylovora.