Epidemiology and Genetic Diversity of Grapevine Leafroll-Associated Viruses in British Columbia

Abstract

Grapevine leafroll disease (GLD) is a complex associated with one or more virus species belonging to the family Closteroviridae. The majority of viruses in this complex are vectored by one or more species of mealybugs (Pseudococcidae) and/or scale insects (Coccidae). Grape-growing regions of British Columbia (BC), including Okanagan, Similkameen, and Fraser valleys and Kamloops (BC central interior), Vancouver, and Gulf islands, were surveyed during the 2014 and 2015 growing seasons for the presence of four major grapevine leafroll-associated viruses, including Grapevine leafroll-associated virus 1 (GLRaV-1), GLRaV-2, GLRaV-3, and GLRaV-4. In total, 3,056 composite five-vine samples were collected from 153 Vitis vinifera and three interspecific hybrid vineyard blocks. The results showed GLRaV-3 to be the most widespread, occurring in 16.7% of the composite samples, followed by GLRaV-4 (3.9%), GLRaV-1 (3.8%), and GLRaV-2 (3.0%). Mixed infections of two or more GLRaVs were found in 4.1% of the total samples. The relative incidence of GLRaVs differed among regions and vineyard blocks of a different age. Characterization of partial CO1 region from a total of 241 insect specimens revealed the presence of Pseudococcus maritimus, Parthenolecanium corni, and other Pulvinaria sp. in BC vineyards. Spatial patterns of GLRaV-3 infected grapevines in three vineyard blocks from three different regions in the Okanagan Valley showed variable degrees of increase in disease spread ranging from 0 to 19.4% over three growing seasons. Regional differences in the relative incidence and spread of GLD underline the need for region-based management programs for BC vineyards.

Survey for major viruses in commercial Vitis vinifera wine grapes in Ontario

“…As such, they could serve as reservoirs of viruses for infecting commercial wine grape vineyards through vector transmission. While this survey as well as the two surveys conducted in British Columbia [ 11 , 18 ] provided compelling evidence for the wide distribution of major viruses in vinifera wine grapes, virtually no information is available pertaining to the distribution of viruses among non-vinifera grapes. We are currently conducting surveys for major viruses in these non-vinifera grapes in order to obtain a holistic assessment on the scope and magnitude of viral diseases in Ontario.…”

“…It is important to note that much higher prevalence of both GLRaV-3 and GRBV was detected in Ontario compared to British Columbia. For instance, only 1.6% of the 2000 samples tested positive for GRBV in British Columbia [ 11 ] while GLRaV-3 was detected in < 17% of V. vinifera wine grape samples [ 18 ]. Possible reasons for these discrepancies may include differences in the infection status of propagating materials used to establish vineyards, difference in the duration and efficiency of transmission by insect vectors, and efficiencies of nucleic acid isolation systems and test methods.…”

“…However, it remains unknown if it is the only vector or one of the vectors that transmit GRBV in nature. In a recent study, Poojari et al [ 18 ] demonstrated the presence of grape mealybug ( Pseudococcus maritimus ), the soft scale insect Parthenolecanium corni and likely other species in British Columbia. The grape mealybug and cottony maple scale ( Neopulvinaria innumerabilis ) were also detected in Ontario (McFadden-Smith, personal communication).…”

“…Though over 85% the samples included in this survey were collected from Ontario, only a small percentage of these samples (20.9%) were from V. vinifera cultivars. Two recent surveys were conducted in British Columbia on the distribution and genetic diversity of GRBV [ 11 ] and four viruses associated with leafroll disease [ 18 ]. GLRaV-3 was shown to be the most prevalent, being detected in 16.7% of composite samples, whereas GLRaV-1, − 2 and − 4 were detected in a small percentage of samples (< 4%).…”

A Diverse Virome of Leafroll-Infected Grapevine Unveiled by dsRNA Sequencing

“…Incidences of infestation range from 0.06% to 12.2%. Recently, Poojari et al conducted studies on the incidence of GLR and GRBV in BC [ 16 , 17 ] and surveyed for GLR, GFL, GRBV, Grapevine pinot gris virus (GPG) in NS vineyards in V. vinifera and Vitis interspecific hybrids [ 13 ]. In addition, GLR-3 and GRBV were observed in ON vineyards by Xiao et al [ 18 ] in a study aiming at improving methods to detect viruses for use in diagnostics.…”