Phylogenetic analysis of Grapevine virus A virus from the vineyards of Khorasan Razavi province based on partial ORF5 gene

Grapevine virus A (GVA) belongs to Vitivirus genus and is one of the most important causes of wood rugose in grapes. During the years 2019 to 2021, a total of 79 leaf samples showing symptoms of leaf yellowing and reddening from vineyards of Khorasan Razavi Province (including Bardaskan, Kashmar, Khalilabad, and Mohammadiyeh) were collected. The initial infection of the samples to GVA was directly checked using an ELISA test, and the final confirmation of results was performed by RT-PCR with specific primers. Total RNA extraction was performed from scraped bark of young stems using CTAB method. GVA was detected in 14 samples through the ELISA test, and a fragment of 238 base pairs from the p10 protein was amplified in these 14 samples using RT-PCR. The amplified products from four samples were ligated into the pTG19-T vector, and the recombinant plasmids were sequenced bidirectionally. The obtained sequences were compared with the other GVA sequences in GenBank using BlastN tool and the nucleotide similarity was 85.7-95%. The phylogenetic tree based on p10 protein showed there are four main groups, and Khorasan Razavi isolates classified within the fourth group. Comparison of p10-protein sequence of Iranian isolates with other isolates showed there is a conserved region in N-terminal region, which includes an arginine-rich motif followed by a zinc-finger motif. There have been many studies on other viruses of grape in this province, but this is the first study on ithe phylogenyof GVA isolates in the vineyards of Khorasan Razavi province.