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The aim of this study was to develop a rapid, sensitive and reliable field-based assay for detection of the quarantine pathogen Pseudomonas syringae pv. actinidiae (Psa), the causal agent of the most destructive and economically important bacterial disease of kiwifruit. A comparative genomic approach was used on the publicly available Psa genomic data to select unique target regions for the development of two loop-mediated isothermal amplification ( LAMP) assays able to detect Psa and to discriminate strains belonging to the highly virulent and globally spreading Psa biovar 3. Both LAMP assays showed specificity in accordance with their target and were able to detect reliably 125 CFU per reaction in less than 30 min. The developed assays were able to detect the presence of Psa in naturally infected kiwifruit material with and without symptoms, thus increasing the potential of the LAMP assays for phytosanitary use. [ABSTRACT FROM AUTHOR]

Erwinia piriflorinigrans is a newly described pathogen causing necrosis of pear blossoms. Complete sequencing of the 37-kb plasmid pEPIR37 common to 27 E. piriflorinigrans strains revealed homology to sequences of the ubiquitous plasmids p EA29 of the fire blight pathogen E. amylovora, plasmid p EP36 of E. pyrifoliae, plasmid p EJ30 of Erwinia sp. from Japan, and genomic regions of the related Rosaceae epiphytic Erwinia species E. tasmaniensis and E. billingiae. A second 5·5-kb cryptic plasmid p EPIR5, found in 12 E. piriflorinigrans strains, was also sequenced revealing mobilization and replication proteins with similarities to many small Col E1-type plasmids in Erwinia spp. and other enterobacteria. Functional analyses of p EPIR37 introduced into a strain of E. amylovora cured of p EA29 plasmid, which has a reduced virulence, showed a role in increasing symptom development similar to that observed in E. amylovora carrying plasmid p EA29. [ABSTRACT FROM AUTHOR]