Incidence, Biological Properties and Phylogenetic Status of Potato Virus A Isolates in Khorasan-e-Razavi and Markazi Provinces Based on Coat Protein Gene

Potato virus A is one of the most important viruses infecting potato in the world. During spring and summer of the year 2011، a total of 280 symptomatic and 463 random leaf samples، and 1186 tuber samples were collected from potato fields located in Khorasan-e-razavi and Markazi provinces، Iran and tested for PVA infection using DAS-ELISA method. Based on the results obtained، PVA infection was recorded in 39 and 11 % of symptomatic leaf samples، 23 and 6 % of random leaf samples and 17 and 13 % tuber samples in Markazi and Khorasan-e-Razavi provinces، respectively. Morever، biological properties of the selected PVA isolates were studied using host range studies on 10 plant species. Four PVA isolates were selected and their coat protein (CP) gene was amplified by specific primers using RT-PCR and their nucleotide sequences were determined (KF152950-3). The CP sequences of four Iranian and 37 Non-Iranian (from other parts of the world) PVA isolates were compared and a phylogenetic tree was reconstructed using Neighbor Joining-NJ method with 1000 bootstrap value. The PVA isolates in the phylogenic tree were clustered in two main groups (I and II) where group I had two subgroups (IA and IB). Three Iranian PVA isolates (Ar2، Kh4 and F2 all from Markazi province) were grouped in IA subgroup and showed highest similarity with two isolates from Germany and Netherlands (Y11427 and X91968) and the other Iranian PVA isolate (Gh4 from Khorasan-e-Razavi P.) was grouped in IB subgroup showing the highest similarity with an isolate from China (DQ309063). Comparison of the deduced amino acid (aa) sequences of CP among the four Iranian and the other PVA isolates revealed substitution of 2 to 7 aa mainly in N terminal of CP. This is the first phylogenetic study on Iranian PVA isolates and also the first report of PVA infection in Markazi province. This study showed variation among PVA isolates in Iran. These data could to be considered in potato breeding programs in order to achieve PVA resistant cultivars.