Identification of Ilarviruses in almond and cherry fruit trees using nested PCR assays

In this study nested PCR assays have been developed for the detection of Prune dwarf virus (PDV), Prunus necrotic ringspot virus (PNRSV) and Apple mosaic virus (ApMV) modifying a previously reported assay for the generic detection of ilarviruses. In all cases one generic upstream primer was used along with a virus-specific downstream primer in respective nested PCR assays. The application of the same thermocycling profile allowed all amplifications to run in parallel. Ilarvirus isolates from different hosts were used for the evaluation of the detection range of the assays, which were afterwards applied for screening almond and cherry plant material. In almond trees the incidence of PNRSV and PDV was 41% and 21.5%, respectively. In cherry orchards the opposite was observed with PDV (56.6%) being the prevalent virus followed by PNRSV (19.4%). Mixed infections with both viruses were also encountered in approximately 10 and 17% of cherry and almond trees, respectively. ApMV was not detected in any of the samples tested. This is the first extensive survey conducted in Greece in order to monitor the distribution of these viruses using molecular assays.