DETECTION AND VARIABILITY OF OLIVE LATENT VIRUS 3 IN THE MEDITERRANEAN REGION
A. Alabdullah, T. Elbeaino, A. Minafra, M. Digiaro, G.P. Martelli
RT-PCR and dot blot hybridization assays were successfully used for the detection of Olive latent virus 3 (OLV-3), a newly discovered olive-infecting virus belonging to the family Tymoviridae. To assess the geographical distribution of OLV-3, a total of 224 olive samples were collected from eight Mediterranean countries and tested by RT-PCR and dot blot hybridization. According to RT-PCR assay, OLV-3 was detected in all surveyed countries with an overall average infection of 30.4%, ranging from 17% (Portugal) to 56% (Turkey). In 12 of 68 samples (c. 20%) shown to be infected by RT-PCR, dot blot hybridization failed to detect the virus, possibly because of the low concentration of target RNA. Single strand conformation polymorphism (SSCP) analysis of the viral RNA dependent RNA polymerase (RdRp) domain, conducted on the 68 PCR amplicons from infected trees of different geographical origin, yielded eleven heterogeneous patterns. Computerassisted analysis of the RdRp nucleotide sequences showed that the level of variability among the isolates ranged from 5% to 17%. In a tree constructed with RdRp nucleotide sequences, viral isolates grouped into three distinct clusters with no relation to their geographical origin. Even though preliminary, the results of the field survey indicate that OLV-3 ranks among the most widespread olive-infecting viruses in the Mediterranean basin.