Biological, Serological, and Molecular Characterization of a Highly Divergent Strain ofGrapevine leafroll-associated virus 4Causing Grapevine Leafroll Disease

Abstract

The complete genome sequence of a highly divergent strain of Grapevine leafroll-associated virus 4 (GLRaV-4) was determined using 454 pyrosequencing technology. This virus, designated GLRaV-4 Ob, was detected in Vitis vinifera 'Otcha bala' from our grapevine virus collection at Agroscope. The GLRaV-4 Ob genome length and organization share similarities with members of subgroup II in the genus Ampelovirus (family Closteroviridae). Otcha bala was graft-inoculated onto indicator plants of cultivar Gamay to evaluate the biological properties of this new strain, and typical leafroll symptoms were induced. A monoclonal antibody for the rapid detection of GLRaV-4 Ob by enzyme-linked immunosorbent assay is available, thus facilitating large-scale diagnostics of this virus. Based on the relatively small size of the coat protein, the reduced amino acid identity and the distinct serological properties, our study clearly shows that GLRaV-4 Ob is a divergent strain of GLRaV-4. Furthermore, molecular and serological data revealed that the AA42 accession from which GLRaV-7 was originally reported is in fact co-infected with GLRaV-4 Ob and GLRaV-7. This finding challenges the idea that GLRaV-7 is a leafroll-causing agent.

Relative Prevalence of Grapevine Leafroll-Associated Virus Species in Wine Grape-Growing Regions of California

“…As a consequence, the relative prevalence of the vector-transmitted GLRaV-1, GLRaV-3, and GLRaV-4LV would increase in established vineyards; therefore the use of certified material may lead to changes in the viral profile in vineyards. GLRaV-3 is considered the most important GLD-associated virus in most grape-growing regions worldwide [ 12 , 22 , 29 – 37 ]. Similarly, GLRaV-3 was the most commonly detected species in this study; however, it is not known why GLRaV-3 is associated with most vector-mediated epidemics of GLD in different countries in the world, while GLRaV-1 and GLRaV-4LV are less problematic [ 3 ].…”

“…Finally, Grapevine leafroll-associated virus 7 (GLRaV-7) is a member of the newly proposed genus Velarivirus . There are no vectors identified for GLRaV-7, and its role in GLD has been recently questioned [ 12 , 13 ]. Thus, GLD is associated with several viral species that have broad biological differences, including varying associations with disease symptoms and insect vectors.…”

Molecular characterization of divergent closterovirus isolates infecting Ribes species

“…The genome identity of the BcLRaV-1 isolates resembles those of grapevine leafroll-associated viruses 3 and 4, members of the genus Ampelovirus [28,28] with values of 62 % and 68 %, respectively. For members of Closterovirus genus, the most distant examples could be found among CTV and GLRaV-2, whose isolates share 79 % and 72 % of overall nt identities, respectively.…”

Molecular characterization of a grapevine leafroll-associated virus 4 from Slovenian vineyards

“…GLRaV-4 has been reported from many grapevine-growing countries worldwide (Martelli, 2014). In Europe it was reported from Portugal (Esteves et al, 2012), Spain (Padilla et al, 2010), France (Th ompson et al, 2012), Switzerland (Reynard et al, 2015), Italy (Giampetruzzi et al, 2011;Rizzo et al, 2014), Greece (Maliogka et al, 2008) and Turkey (Buzkan et al, 2010). Except Switzerland, there are no reports of GLRaV-4 from Central and Eastern Europe.…”