Characterization of grapevine leafroll-associated virus 3 genetic variants and application towards RT-qPCR assay design

Grapevine leafroll-associated virus 3 (GLRaV-3) is the most widely prevalent and economically important of the complex of RNA viruses associated with grapevine leafroll disease (GLD). Phylogenetic studies have grouped GLRaV-3 isolates into nine different monophyletic groups and four supergroups, making GLRaV-3 a genetically highly diverse virus species. In addition, new divergent variants have been discovered recently around the world. Accurate identification of the virus is an essential component in the management and control of GLRaV-3; however, the diversity of GLRaV-3, coupled with the limited sequence information, have complicated the development of a reliable detection assay. In this study, GLRaV-3 sequence data available in GenBank and those generated at Foundation Plant Services, University of California-Davis, was used to develop a new RT-qPCR assay with the capacity to detect all known GLRaV-3 variants. The new assay, referred to as FPST, was challenged against samples that included plants infected with different GLRaV-3 variants and originating from 46 countries. The FPST assay detected all known GLRaV-3 variants, including the highly divergent variants, by amplifying a small highly conserved region in the 3' untranslated terminal region (UTR) of the virus genome. The reliability of the new RT-qPCR assay was confirmed by an enzyme linked immunosorbent assay (ELISA) that can detect all known GLRaV-3 variants characterized to date. Additionally, three new GLRaV-3 divergent variants, represented by four isolates, were identified using a hierarchical testing process involving the FPST assay, GLRaV-3 variant-specific assays and high-throughput sequencing analysis. These variants were distantly related to groups I, II, III, V, VI, VII and IX, but much similar to GLRaV-3 variants with no assigned group; thus, they may represent new clades. Finally, based on the phylogenetic analysis, a new GLRaV-3 subclade is proposed and named as group X.Alfredo Diaz-Lara, Vicki Klaassen, Kristian Stevens, Mysore R. Sudarshana, Adib Rowhani ... Nuredin Habili ... et al

Charging of deformed semicrystalline polymers observed with a scanning electron microscope

10.1109/94.484316IEEE Transactions on Dielectrics and Electrical Insulation261123-1131ITDI

Effect of conjugated bonds on the charging of insulating polymers

10.1063/1.357590Journal of Applied Physics7642414-241

Grapevine virus I, a putative new vitivirus detected in co-infection with grapevine virus G in New Zealand

A novel virus, with characteristics of viruses classified within the genus Vitivirus, was identified from a sample of Vitis vinifera cv. Chardonnay in New Zealand. The virus was detected with high throughput sequencing (small RNA and total RNA) and its sequence was confirmed by Sanger sequencing. Its genome is 7507 nt long (excluding the polyA tail) with an organisation similar to that described for other classifiable members of the genus Vitivirus. The closest relative of the virus is grapevine virus E (GVE) with 65% aa identity in ORF1 (65% nt identity) and 63% aa identity in the coat protein (66% nt identity). The relationship with GVE was confirmed with phylogenetic analysis, showing the new virus branching with GVE, Agave tequilina leaf virus and grapevine virus G (GVG). A limited survey revealed the presence of this virus in multiple plants from the same location where the newly described GVG was discovered, and in most cases both viruses were detected as co-infections. The genetic characteristics of this virus suggest it represents an isolate of a new species within the genus Vitivirus and following the current nomenclature, we propose the name “Grapevine virus I”