The Occurrence of Grapevine Fanleaf Virus in Washington State Vineyards

Grapevine degeneration in grapevines caused by Grapevine fanleaf virus (GFLV) has been documented in many viticultural regions worldwide (Andret-Link et al. 2004). It is one of the major economically important virus diseases affecting the longevity of grapevines and reducing the fruit yield and fruit quality. Infected grapevines show a range of foliar symptoms consisting of leaf deformation, yellow mosaic, vein banding, ring and line patterns and flecks. GFLV cause yield reductions as high as 80% depending on the cultivar and severity of infection (Martelli and Savino 1990). Plant-to-plant spread of GFLV is known to occur by dagger nematode (Xiphinema index) and hence the infected grapevines appear in patches in the field. Long distance spread of the virus, however, occurs by transfer of infected propagation material. GFLV (genus: Nepovirus, family Comoviridae) has a bipartite genome consisting of two single-stranded, positive sense RNAs called RNA-1 and RNA-2 (Pink et al., 1988). Genetic diversity of GFLV genome has been studied in different countries (Arani et al. 2001; Vigne et al., 2004; Pompe-Noak et al., 2007), thereby establishing quasi-species nature of the virus.