An Indigenous Virulent Strain of Erwinia amylovora Lacking the Ubiquitous Plasmid pEA29

Abstract

An atypical strain of Erwinia amylovora was isolated near an outbreak of fire blight at a nursery in Spain in 1996. It was obtained from a Crataegus plant showing typical symptoms and was identified as E. amy-lovora by biochemical tests and enrichment-enzyme-linked immuno-sorbent assay, but not by polymerase chain reaction using primers based on the pEA29 sequence. Nevertheless, with primers from chromosomal regions, the isolate gave the expected amplification band. This strain carries one plasmid of approximately 70 kb, with no homology with the 29-kb plasmid common to all pathogenic strains, or with a large plasmid present in some E. amylovora strains. Growth of the strain in minimal medium without thiamine was slower compared with cultures in the same medium with thiamine, a characteristic typical of strains cured of the 29-kb plasmid. Nevertheless, aggressiveness assays on pear, apple, and Pyracantha plants and in immature pear fruit showed that this strain exhibited a virulence level similar to other strains containing pEA29. To the best of our knowledge, this is the first report of the isolation from naturally infected plant material of a pathogenic strain of E. amylovora without pEA29, but with a plasmid of approximately 70 kb not previously described.

Characterizationof Moroccan Population of ErwiniaAmylovora, the Causal Agent of Fire Blighton Rosacea

“…On diagnosis, this result shows that only the primers as pEA71, EaIsc are reliable. In addition, other strain of fire blight reported absence of plasmid pEA29 [24], [25].…”

Characterisation of naturally occurring Erwinia amylovora strains lacking the common plasmid pEA29 and their detection with real-time PCR

“…in Spain and is obviously related to strain IVIA1614-2a, which was isolated from Crataegus sp. and also described as lacking plasmid pEA29 (Llop et al 2006). Isolation of these strains without pEA29 from different sites or from different host plants supports their natural existence.…”

“…Occasionally, the transposon was delivered into pEA29 visible by band shifts in plasmid fragments and created a convenient label in the plasmid for genetical manipulations. Additional plasmids have been described for E. amylovora, and a 70 kb plasmid was assumed to compensate for a lack of pEA29 (Llop et al 2006). In this study, we screened E. amylovora strains from various geographic origins for the presence of pEA29 and describe strains, where neither pEA29 nor any other plasmid could be detected.…”

Phenotypic and genetic diversity of Erwinia amylovora: the causal agent of fire blight

“…Such a reaction may indicate an earlier acquisition of pEA29 from E. amylovora. By contrast, a few isolates of E. amylovora without this plasmid were found in Egypt, Iran, Spain and the USA (Carey et al 2011;Llop et al 2006;Mohammadi et al 2009). Also, it was found that another plasmid of approximately 65 kb (pEI70) present in one of these isolates, showed no homology with pEA29.…”