In summer 2011, 137 samples were collected from vines showing YS and VB, as well from vines without such symptoms in West-Azarbaijan, East-Azarbaijan and Ardabil provinces (North-West Iran). Total nucleic acids (TNA) were extracted according to a protocol by Foissac et al. (2000) with minor modifications as described by Hajizadeh et al. (2012). Reverse transcription (RT) was done with random hexamer primers and polymerase chain reaction (PCR) with the specific primer pair GYSVd-1 and GYSVd-2 as described in Wan Chow Wah and Symons (1997) using Pfu DNA polymerase. The same RNA preparations from the 137 grapevines which were tested for viroid infection were further assayed for GFLV by RT-PCR using the specific primer pair designed by MacKenzie et al. (1997). RT-PCR showed that GYSVd-1 and GYSVd-2 occurred in 125 (91%) and 87 (64%) of the samples, respectively. GFLV was detected in 37% of the samples, confirming the previously reported widespread occurrence of this virus in north-west Iran (Sokhandan-Bashir et al., 2007). VB was observed in 22 vines all of which were also infected by GYSVd-1, GYSVd-2 and GFLV, thus confirming previous reports on concurrence of these different agents in the etiology of this syndrome (Szychowski et al., 1995). YS symptoms (Fig. 1A), which occurred in about 10% of the tested plants, were shown to be always associated with vines infected by GYSVd-1 and/or GYSVd-2. These findings are in line with the notion that assigns to GYSVd-1 and GYSVd-2 a role in the induction of YS, and to both viroids and GFLV the genesis of VB.
