New Plum pox virus foci in campania and Basilicata (Southern Italy)

During the last decade stone fruits orchards in Southern Italy have suffered extended and severe outbreaks of Sharka disease mainly caused by Plum pox virus (PPV) D isolates. An extensive survey in several stone fruit orchards of Salerno (Campania) and Matera (Basilicata) provinces, was conducted aiming at the identification of new PPV foci over an area of 500 ha. Nearly 20,000 plants between apricot, plum, peach and nectarines were observed for the presence of symptoms. About 1000 plants that showed symptoms of viral infection were analysed by DAS-ELISA using PPV-specific polyclonal antibodies, 2% of which proved to be infected by PPV. Virus isolates responsible of the infection were characterised by biological indexing, by ELISA using monoclonal antibodies specific to the four strains and finally by RT-PCR, followed by AluI and RsaI RFLP analysis. All viral isolates belonged to the PPV-D subgroup. Two PPV-D isolates from different provinces, Salerno and Matera, selected for molecular characterisation, consisting in the amplification, cloning and sequencing of the CP gene, shared a similarity of about 100%, indicating that the identified foci were caused by the same PPV isolate. In May 2007, two new severe PPV foci were identified at Nocera Inferiore (SA) and on the Ionian coast of Basilicata, both on apricot cv. Ninfa. Virus isolates responsible for infection are under investigation.