Serological and molecular detection of Potato virus S (PVS) from common potato cultivars in Ardabil province

Potato virus S (PVS) of the genus Carlavirus belongs to the Betaflexiviridae family is one of the important potato infectious viruses. To detect PVS, the suspected leaf samples were collected from potato fields in Ardabil province during summer in 2015 and 2016. To assess the biological properties, symptomatic leaves inoculated to indicator plants in the greenhouse condition. The samples were tested for PVS infection using DAS-ELISA. RT-PCR for molecular detection was done using specific primers related to the coat protein area of Potato virus S. The coat protein gene nucleotide sequences of two isolates of Potato virus S called Ag-9 and Os-11 obtained from Agria and Oceana cultivars were determined. The CP sequences of two isolates were compared with each other and with 29 other isolates of the virus. The reconstructed phylogenetic tree clustered the isolates in two main groups I (subgroups IA and IB) and II. Two Ag-9-PVS-F and Os-11-PVS-F isolates were clustered in IB subgroup along with isolates from Azarbaijan, Hamedan, Kerman and Esfahan as well as isolates from Hungary, Ukraine, Scotland and India. The putative coat protein amino acid sequence alignment of this two isolates with 6 Iranian and 5 foreigner isolates showed difference in 8 and 25 amino acids for Ag-9-PVS-F and Os-11-PVS-F isolates respectively. The results indicate that there are various PVS isolates in the country, and the difference in nucleotide and amino acid sequences may indicate differences in the geographic origin and hence the type and timing of entry of virus isolates into the region.