Distinct Red Blotch Disease Epidemiological Dynamics in Two Nearby Vineyards

• Published in: Viruses 2023-05, Vol.15 (5), p.1184
• Main Authors: Flasco, Madison T, Cieniewicz, Elizabeth J, Pethybridge, Sarah J, Fuchs, Marc F
• Format: Article
• Language: English
• Subjects: Blotch; Coronaviruses; COVID-19; Cultivars; Disease transmission; Diseases and pests; Distribution; Epidemiology; Farms; Geminiviridae; Genetic aspects; Genomes; Grablovirus; Grapes; grapevine red blotch virus; Pandemics; Phylogenetics; Phylogeny; Plant Diseases; Plant viruses; Planting; Polls & surveys; spatial analysis; Spissistilus festinus; Vines; Vineyards; Virus diseases of plants; Virus research; Vitis; Vitis vinifera; Wineries & vineyards
• ISSN: 1999-4915; 1999-4915
• DOI: 10.3390/v15051184

Grapevine red blotch virus (GRBV) causes red blotch disease and is transmitted by the three-cornered alfalfa hopper, . GRBV isolates belong to a minor phylogenetic clade 1 and a predominant clade 2. Spatiotemporal disease dynamics were monitored in a 1-hectare 'Merlot' vineyard planted in California in 2015. Annual surveys first revealed disease onset in 2018 and a 1.6% disease incidence in 2022. Ordinary runs and phylogenetic analyses documented significant aggregation of vines infected with GRBV clade 1 isolates in one corner of the vineyard ( = -4.99), despite being surrounded by clade 2 isolates. This aggregation of vines harboring isolates from a non-prevalent clade is likely due to infected rootstock material at planting. GRBV clade 1 isolates were predominant in 2018-2019 but displaced by clade 2 isolates in 2021-2022, suggesting an influx of the latter isolates from outside sources. This study is the first report of red blotch disease progress immediately after vineyard establishment. A nearby 1.5-hectare 'Cabernet Sauvignon' vineyard planted in 2008 with clone 4 (CS4) and 169 (CS169) vines was also surveyed. Most CS4 vines that exhibited disease symptoms one-year post-planting, likely due to infected scion material, were aggregated ( = -1.73). GRBV isolates of both clades were found in the CS4 vines. Disease incidence was only 1.4% in non-infected CS169 vines in 2022 with sporadic infections of isolates from both clades occurring via secondary spread. Through disentangling GRBV infections due to the planting material and -mediated transmission, this study illustrated how the primary virus source influences epidemiological dynamics of red blotch disease.