To gain an insight into presence of HSVd in grapevine, during 2011-213, 154 samples were collected from North-West (West-Azerbaijan, East-Azerbaijan and Ardabil Provinces)and West (Kurdistan Province) of Iran.Total nucleic acid was extracted from leaves by the silica-capture method (Foissacet al., 2000) and used as template for reverse transcription polymerase chain reaction (RT-PCR). RT-PCR showed that all of the assayed 154 Iranian vines were infected by HSVd. On the other hand, high incidence of HSVd in Japan (88%) (Sano et al., 1986), Czech Republic (70%) (Matouseket al., 2003) have also been recorded. Therefore, it seems that this viroid passess widespread in many places of the world. Due to the widespread prevalence of HSVd in most grapevine cultivars (100% in the west and northwestern region of Iran), we propose to use this viroid as an internal control in surveying the vine for presence of viroids and viruses in grapevine by RT-PCR. An advantage of this choice is that HSVd shares many structural characteristics with the other grapevine viroids and, contrary to internal controls derived from host mRNAs or rRNAs (Gambino et al., 2009), no DNase treatment is needed prior to reverse transcription. This saves time and costs when performing the diagnostic system. For the same reasons, HSVd could be a feasible internal control for RT-PCR multiplex protocols for detection of viroids (Hajizadeh et al., 2012) and RNA viruses in grapevines as well.
