Analysis of the genetic diversity of Grapevine rupestris stem pitting-associated virus in Ontarian vineyards and construction of a full-length infectious clone

Abstract

Grapevine rupestris stem pitting-associated virus (GRSPaV; Betaflexiviridae, Foveavirus) has been associated with a number of diseases including Syrah decline. Previous findings show GRSPaV sequence variants cluster into three or more main phylogroups, regardless of geographical location. Here, the genetic diversity of GRSPaV isolates from Ontarian vineyards was analyzed using broad-spectrum primers targeting the viral polymerase coding sequence. It was hypothesized that GRSPaV variants in Ontario are diverse and GRSPaV-SY variants are involved in Syrah decline symptoms. In total, 169 cDNA clones from 21 Vitis sources were used for phylogenetic analysis. Similarly to previous reports, four major lineages were observed; GRSPaV-PN, -SG1, -SY, and –GG. Variants of the GRSPaV–SY lineage were confirmed in all 14 sources tested with SY-specific primers. Syrah cultivars expressing red canopy decline symptoms had more clones clustering with the GRSPaV-SY lineage than those without observable decline symptoms. GRSPaV clones from 8 hybrid sources mostly clustered with GRSPaV-SY, followed distantly by GRSPaV-BS. A full-length infectious cDNA clone of a GRSPaV-SY-related variant is being constructed to further investigate this relationship.