Distribution and population diversity of Australian grapevine viroid (AGVd) in Turkish autochthonous grapevine varieties

Several viroid species have been reported to infect grapevine in Turkey and there has been not much about their genetic diversity, except Australian grapevine viroid (AGVd, genus Apscaviroid, family Pospiviridae). The viroid was recently detected in Turkish vineyards with very little information about its variability. Therefore, the autochthonous grapevine varieties in two major grape-growing areas in Turkey, i.e. the Eastern Mediterranean and the Southeast Anatolia regions were tested for the prevalance and genetic diversity. The presence of AGVd in the autochthonous varieties was verified by RT-PCR. The incidence of AGVd infection was relatively low in both regions due to self-rooted nature of the plants in the areas. Comparative analysis of local AGVd isolates from these native varieties was performed with viroidal genome sequences from NCBI database. Consequently, AGVd populations in Turkey contained five major sequence variants consisting of three varieties. Four variants had minor sequence variations while one was remarkably diverse.