Julia Hooker and Baozhong Meng*
*University of Guelph, 50 Stone Road East, Guelph, Ontario, N1G2W1, Canada (bmeng@uoguelph.ca)

Grapevine rupestris stem pitting-associated virus (GRSPaV; family Betaflexiviridae, genus Foveavirus) is a positive-sense, single-stranded RNA virus detected in grapevines worldwide. While definitive proof is still lacking, different strains of GRSPaV are associated with several grapevine diseases such as Rupestris Stem Pitting, Vein Necrosis, and Syrah Decline. Sequence variants of this virus form distinctive clusters and different clusters may correlate with different diseases. To improve understanding of the genetic diversity and pathological properties of GRSPaV, we analyzed the genetic diversity of viral sequence variants present in Ontarian vineyards. It was hypothesized that multiple sequence variants of GRSPaV are present in Ontarian vineyards and that variants of the –SY lineage, either alone or in combination with other agents, are responsible for the observed Syrah Decline syndrome. Using reverse-transcriptase polymerase chain reaction, genomic regions of the RNA-dependent RNA polymerase and the capsid protein were cloned, sequenced, and subjected to phylogenetic analysis. The vast majority of viral clones from table and juice varieties clustered with GRSPaV-SY, while some clustered with -VF1. In winegrape varieties, those with and without observable Decline symptoms had similar groups of variants overall. However, most clones derived from grapevines without observable symptoms clustered with -SY and -JF lineages. In symptomatic grapevines, the majority of clones clustered with the -SY and -VF1 groups, suggesting that these clusters of sequence variants may be involved with symptoms. A full-length cDNA clone corresponding to GRSPaV-SY is being constructed and its infectivity will be assayed in Nicotiana benthamiana and the natural host, grapevine. We hope that these studies will provide new insight into a potential correlation between certain viral variants and the Syrah Decline symptoms observed in Ontarian vineyards.

Funding Support: NSERC Engage Grant, NSERC Discovery Grant