Grapevine vein clearing virus: Diagnostics, genome, genetic diversity, and management

Abstract

Grapevine vein clearing virus (GVCV) is a recently discovered DNA virus that is closely associated with a severe disease that poses a great threat to the sustainable growth and productivity of grapevines in the Midwest region of the USA. The most damaged vineyards have been removed because of GVCV infection. Diagnostic symptoms are translucent vein clearing along the second and tertiary veins on young leaves and mosaic patterns on mature leaves of the affected grapevine. GVCV genome comprises a circular, double-stranded DNA, which is characteristic of the viruses in the genus Badnavirus, family Caulimoviridae. Three large open reading frames (ORFs) are predicted on the plus-strand of the genome. The promoter region and transcription start and termination sites have been mapped. GVCV is replicated through transcription of a terminally redundant transcript as other members of the Caulimoviridae family. Increasing incidences of GVCV on grapevines over the last few years suggest the transmission of the virus by a vector, whose identity is still under investigation. Two new isolates of GVCV were also found in wild grapevines native in Missouri (USA). The reservoirs of genetically complex GVCV populations in wild grapevines create challenges to the management of GVCV-associated disease. The rising prevalence of GVCV and the severity of the emerging disease with which this virus is associated with warrant that it should be tested routinely in the grapevine certification program.