FURTHER MOLECULAR CHARACTERIZATION OF PSEUDOMONAS SYRINGAE pv CORYLI
S. Loreti, F. Gervasi, A. Gallelli, M. Scortichini
The aim of this paper was to further investigate some molecular features of Pseudomonas syringae pv. coryli, the causal agent of hazelnut bacterial twig dieback, and to assess its genetic relationship with some other phytopathogenic pseudomonads of various genomospecies (sensu Gardan et al., 1999). The characterization was done by cloning and sequencing some key genes utilized in taxonomical studies and/or in plant-pathogen interaction such as 16S rDNA, hrpL, as well as the effector genes of the pathogenicity island and the phaseolotoxin tox gene cluster of Pseudomonas syringae pv. phaseolicola. Analysis of hrpL and 16S rDNA genes with Mega 3.1 software and the neighbor-joining clustering algorithm showed a relationship of P. syringae pv. coryli with pseudomonads of genomospecies 1, suggesting its inclusion into this group. Investigation of effector and phaseolotoxin genes showed the inconsistent presence of these genes in some P. syringae pv. coryli strains. Neither the effectors nor the PCR product related to the tox gene cluster of P. syringae pv. phaseolicola were amplified from the majority of the strains. However, one strain showed the presence of a homologous of avrPphD, and another contained either this effector (avrPphD) or the 1.9 kb fragment of the phaseolotoxin tox gene cluster.