Partial characterization of a divergent isolate of pokeweed mosaic virus from Mississippi

An isolate of pokeweed mosaic virus (PkMV), referred to as MSFR03, collected from southwestern Mississippi was partially characterized biologically and molecularly. The virus induced pinwheel-like inclusions in infected cells of its natural host (Phytolacca americana L.) and was mechanically transmitted to Chenopodium quinoa, provoking localized infections. The viral genome is 9516 nt in size, excluding the 3′-terminal poly(A) tail, and contains a large ORF encoding a 3056 amino acids long polyprotein and a small overlapping PIPO ORF. Phylogenetic analyses of the whole polyprotein grouped PkMV with turnip mosaic virus (TuMV), potato virus A (PVA) and related potyviruses. Pairwise sequence comparisons showed that PkMV-MSFR03 is a distinct molecular variant of the virus, differing by more than 15% in nucleotide sequences with any of the four previously sequenced isolates from Pennsylvania, Maryland, New Jersey and Arkansas. Our data suggest that the PkMV population in the United States is genetically more diverse than previously known.