VARIABILITY OF POTATO SPINDLE TUBER VIROID ISOLATES FROM ORNAMENTAL HOSTS IN SLOVENIA

A survey of Potato spindle tuber viroid (PSTVd) was initiated in Slovenia in December 2006. Out of 398 samples collected between the beginning of the survey and the end of 2010, a quarter tested positive for PSTVd, in particular Brugmansia cordata (1), Solanum jasminoides (88), S. rantonnetii (5), Petunia spp. (3), and S. muricatum (3). Analysis of 96 complete master sequences of Slovene positive samples revealed new variants, although the majority of master sequences were identical to the sequence variant of PSTVd found in S. rantonnetii in Italy (EF459700). A substitution of G to U at position 65 was found in several sequence variants otherwise identical to EF459700. The variability of this site was confirmed by cloning three samples that showed ambiguity at position 65 when the PCR products were sequenced directly. Phylogenetic analyses of Slovene sequence variants and sequence variants from GenBank showed two clearly separated clusters. High variability was observed within each cluster. Although most of the sequence variants from the same ornamental host tended to group together, sequence variants from the same hosts also showed high variability. On the other hand different hosts were found to be infected by the same sequence variant.