Incidence, distribution and genetic diversity of<i>Grapevine red blotch virus</i>in British Columbia

Grapevine red blotch virus (GRBV) is a recently identified virus reported mainly from several grape-growing regions in the USA. To date, no information about the occurrence of GRBV is available in British Columbia (BC). Accordingly, a large-scale survey was conducted across all grape-growing regions of BC to determine the incidence and distribution of GRBV. A total of 2000 composite samples representing nine white and eight red Vitis vinifera cultivars from 128 vineyard blocks were tested for GRBV by PCR using virus-specific primers. The results showed that 32 out of 2000 (1.6%) composite samples were positive for GRBV, indicating a low incidence of this virus in BC vineyards. An analysis of the vineyard blocks positive for GRBV revealed that they were established between 2011 and 2014, suggesting a recent introduction of GRBV into BC, probably through infected plant material. Complete genome characterization and phylogenetic analysis of 29 representative GRBV isolates from BC grouped 15 isolates into clade I, sharing less than 95% identity at the nucleotide level, whereas 14 isolates grouped into clade II, sharing more than 95% identity at the nucleotide level. This result was consistent with the presence of both genetic variants in BC vineyards. Putative recombination events were detected among aligned complete genome sequences of BC isolates of GRBV and global isolates of the virus. These findings underscore the need for domestic clean plant propagation programmes and development of long-term management strategies to minimize GRBV spread in BC.