Phylogenetic analysis of Prunus necrotic ring spot virus in pome and stone fruit trees in Kurdistan province

In order to study molecular identification and genetic diversity of Prunus necrotic ringspot virus (PNRSV), 149 leaf samples from 37 orchards of pome and stone fruit trees of Kurdistan province were collected and tested by RT-PCR using a PNRSV-F3/PNRS-R3 specific primer pair. Results showed that 20.8% of the samples were infected by PNRSV.In the next stage of the study, 13 isolateswere selected based on the host and geographic region and their amplified fragments were ligated into the pTG19-T plasmid, transformed to E. coli DH5α, and sequenced. Phylogenetic analysis showed that PNRSV isolates formed three clades PV96, PV32, and PE5, and all new-sequences from Kurdistan (in this research) were categorized in PV96 phylogenetic clade, which is close to other Iranian isolates. The new isolates shared 99 ± 0.002 identities together and 94/9 ± 0.005 with other previously PNRSV reported isolates at the nucleotide level. Pairwise comparisons of sequences showed that isolates peach from Kamyaran (KH10), pear from Sanandaj (SZ93), and peach from Dehgolan (D7) had the highest nucleotide similarity (98%) with Iranian isolate nectarine (KX353935) whereas isolate pear from Sanandaj (SZ26) had the lowest nucleotide identity with isolate plum from Poland (DQ983499). The low dN/dS ratio in all populations of the virus showed that negative selection plays important role in PNRSV-CP evolution and recombination. There is no recombination event in this domain of PNRSV genome of these isolates.