Rupestris stem pitting associated virus-1 consists of a family of sequence variants

Summary

 Rupestris stem pitting (RSP) seems to be one of the most widespread virus diseases of grapevines. A virus, designated as rupestris stem pitting associated virus-1 (RSPaV-1), is consistently associated with, and likely to be the causative agent of RSP. Sequence analyses of cDNA clones derived from several RSP-affected grapevines suggested that a family of sequence variants of RSPaV-1 was associated with RSP. The genome structure of the sequence variants is identical to that of RSPaV-1 in that they had five open reading frames (ORF) and sequence identities ranging from 75 to 93% in nucleotide sequence and from 80 to 99% in amino acid sequence. ORF5 (coat protein) and the carboxyl-terminal portion of ORF1 (replicase) appeared to be the most conserved regions. The coat proteins of the sequence variants exhibited highly similar antigenic indices, suggesting serological relatedness among them. The cDNA clones obtained through reverse transcription-polymerase chain reaction from RSP-infected grapevines were heterogeneous in nt sequence with identities of 77–99% relative to RSPaV-1. Furthermore, a number of sequence variants were identified in several grapevines infected with RSP. Baselines for defining RSPaV-1 and possible mechanisms accounting for infection of grapevines with multiple sequence variants of RSPaV-1 are proposed. Findings from this study should have practical applications toward understanding the etiology of RSP and developing reliable assays to rapidly detect the disease.