P-460 - Survey, molecular characterization and epidemiology of grapevine viruses in Oklahoma

Viruses cause significant diseases and yield losses in grapevine (Vitis spp.) production systems globally, but viruses affecting Oklahoma grown grapes are not well understood. To address this paucity of knowledge, a state-wide virus survey was initiated across vineyards in 2024 to identify and characterize grapevine viruses. Canes and leaf samples were collected from various cultivars for analysis. Total RNA was extracted from cambium and petioles, respectively followed by cDNA synthesis. Each cDNA template was tested by PCR for 11 commonly reported viruses. Four viruses, including grapevine leafroll-associated virus 1 (GLRaV-1), grapevine red blotch virus (GRBV), grapevine virus E (GVE) and grapevine rupestris stem pitting-associated virus (GRSPaV) were identified in the samples with varying levels of incidences on different cultivars. GLRaV-3 and GRBV were predominant, with first reports for GVE and GRSPaV in Oklahoma. Multiple gene fragments per virus were further amplified from positive samples, cloned, and sequenced. Sequence analyses of GLRaV-3 isolates revealed high conservation in the genomic regions, suggesting a recent common ancestor or a limited number of introduction events. Phylogenetic analysis identified GLRaV-3 phylogroups 1, 2, and 5. Analyses of GRBV genomes identified strains belonging to clades I and II, with both normal and divergent clade II strains. A few GLRaV-3 and GRBV strains were identified as putative recombinants. These results are important in understanding the epidemiology of grapevine viruses in Oklahoma.