The Relative Occurrence of Grapevine leafroll-associated virus 3 and Grapevine red blotch virus in Washington State Vineyards

Abstract

Vineyard surveys were conducted for three consecutive seasons in east- and 9.06% of samples positive for both viruses. About 17% of samples ern Washington State, the major grapevine-growing region in the state, tested negative for the two viruses, but some of these samples were to document the occurrence of Grapevine leafroll-associated virus 3 positive for GLRaV-2 and GLRaV-4. Overall results indicated that (GLRaV-3) and Grapevine red blotch virus (GRBV). The majority of GLRaV-3 was more common than GRBV, independent of cultivars and samples were collected from red-berried wine grape (Vitis vinifera) culthe geographic origin of samples. Due to variability in symptoms in redtivars exhibiting symptoms of or suspected for grapevine leafroll (GLD) berried cultivars, virus-specific diagnostic assays were deemed necessary and red blotch (GRBD) diseases. A limited number of samples from for reliable identification of GLRaV-3 and GRBV and to differentiate white-berried cultivars were collected randomly due to the lack of visual GLD and GRBD symptoms from those induced by biotic and abiotic symptoms. Samples were collected from a total of 2,063 grapevines from stresses in vineyards. A multiplex PCR protocol was developed for simul-18 red-berried cultivars and seven white-berried cultivars planted in eight taneous detection of GLRaV-3 and GRBV in grapevine samples. A global American Viticultural Areas and tested for GLRaV-3 and GRBV using phylogenetic analysis of GRBV genome sequences revealed segregation of RT-PCR and PCR, respectively. The results showed 67.77% and virus isolates from Washington State vineyards into two distinct clades, 6.01% of total samples positive for GLRaV-3 and GRBV, respectively, with the majority of isolates belonging to clade II.