Biological and Molecular Characterization of an Isolate of Pelargonium Zonate Spot Virus Infecting Sunflower in Argentina

Sunflower (Helianthus annuus) plants showing chlorotic concentric rings and line patterns on the leaves were observed in field crops near Paraná city (Entre Ríos, Argentina). Virus-enriched preparations examined with a trasmission electron microscope contained quasi-spherical particles ca. 33 nm in diameter. Symptomatic sunflower samples were serologically negative for six known members of the family Bromoviridae when tested with commercial antisera, but in later tests gave a positive reaction with a Pelargonium zonate spot virus (PZSV) antiserum. The virus was mechanically transmitted to 16 plant species belonging to four families. Its complete genomic sequence, obtained by pyrosequencing, had an organization typical of members of the family Bromoviridae. Three contigs resulting from de novo assembly of deep sequencing reads showed 90.0%, 94.7% and 93.9% nucleotide identity with RNA-1 (GenBank accession No. AJ272327), RNA-2 (AJ272328) and RNA-3 (AJ272329), respectively, of Pelargonium zonate spot virus (PZSV), a member of the genus Anulavirus described in Italy. Therefore, the virus associated with chlorotic concentric rings and line pattern symptoms in sunflower was identified as an isolate of PZSV. To our knowledge, this is the first reference to PZSV infecting sunflower worldwide and the first report of its presence in South America.