Archivio Journal of Plant Pathology

Abstract:

Genomospecie 8, sensu Gardan et al. (1999), includes Pseudomonas avellanae, P. syringae pv. theae and P. s. pv. actinidiae. To further characterize this genomospecies, 14 P. avellanae, three P. s. pv. theae and 18 P. s. pv. actinidiae strains were analysed by multilocus sequence typing (MLST) using gapA, gltA, gyrB and rpoD gene fragments. These strains were also checked for the presence/absence of 38 effector protein genes based on the corresponding sequences of P. syringae. pv. tomato DC3000 and P. syringae pv. phaseolicola 1448A. Nutritional tests and a comparison of the 16S rDNA gene sequences deposited at NCBI database were also done to detect possible differences. MLST analysis, based on 2.5 kb sequences, revealed that P. s. pv. theae and P. s. pv. actinidiae are more closely-related to one another than to P. avellanae. This technique clearly revealed that the P. s. pv. actinidiae strains causing the current severe epidemics in Italy are different from those of past outbreaks in Japan and central Italy. Nine effector protein genes were displayed by all strains of genomospecies 8. However, each pathogen of this genomospecies displays some distinctive effector protein genes. HopA1 and hopH1 are unique to P. s. pv. actinidiae strains of the recent epidemics of bacterial canker on Actinidia chinensis and A. deliciosa in Italy. A triplet, in position 461-463 of the 16S rDNA gene, is different in P. s. pv. actinidiae, namely GAT, and in P. avellanae and P. s. pv. theae, namely ATC. Contrarily to P. s. pv. theae and P. s. pv. actinidiae, P. avellanae did not utilize sorbitol.