First report of Grapevine red globe virus in grapevine in the United Kingdom

In August 2019 a sample of grapevine (Vitis sp.) leaves was submitted to Fera Science Ltd. from a vineyard in the south of England. The sample was sent following the appearance of an unknown disease. Symptoms included red colouration and flecking (Figures 1, 2). The sample was tested by DAS-ELISA for the presence of Arabis mosaic virus (DSMZ, Germany), Raspberry ringspot virus (DSMZ, Germany), Strawberry latent ringspot virus, Tobacco ringspot virus (Agdia, USA), Tomato black ring virus (DSMZ, Germany and Bioreba, Switzerland), Tomato ringspot virus (Loewe, Germany), and plate trap ELISA for potyviruses using a generic potyvirus antisera (DSMZ, Germany). The sample gave negative results for all tests. The sample was then tested by high throughput sequencing (HTS) on a MiSeq Sequencer (Illumina, UK) (Fowkes et al., 2021). The total number of reads for the sample was 342,422 with 5 (0.001%) being mapped to the genome of Grapevine red globe virus (GRGV, genus Maculavirus). The sequence contig of 217 nt obtained by HTS was checked by nucleotide comparison through BLAST against publicly available sequences. The partial sequence of the replicase gene had 94% identity to a GRGV sequence (GenBank Accession No. MZ451066.1), a historical isolate sequenced from the Sidney live plant collection, country of origin unknown (Mike Rott, CFIA, Pers. Comm.). The genome fragment of GRGV was uploaded to GenBank (ON187032). Sequencing data has been submitted to the NCBI short read archive, BioProject (PRJNA817416). Other grapevine viruses were also inferred from the sequence data, namely Grapevine rupestris stem pitting-associated virus (genus Foveavirus, ON187034) and Grapevine fleck virus (genus Maculavirus, ON187033). In each case these have been previously reported from the UK (Silva et al., 2017). To further confirm infection by GRGV, the sample was tested by RT-PCR using primers specific for GRGV (Ruiz-Garcia et al., 2018). A product of 418 bp was obtained (ON187031). The product was analysed by Sanger sequencing (MWG GmbH, Germany) and checked by nucleotide sequence comparison against sequences publicly available through BLAST. The sequence had 95% identity to the sequence of a GRGV isolate from Washington State, USA (MT749359.1). GRGV was first reported in Italy (Sabanadzovic et al., 2000) and has since been found in China, Croatia, France, Germany, Greece, Iran, Slovenia, Spain and the USA (Nourinejhad Zarghani et al., 2021; EPPO Global database, 2022). No specific symptoms have been associated with GRGV (Ruiz-Garcia et al., 2018), and as the detection of GRGV was in co-infection with other viruses, no conclusion can be drawn on the cause of the observed symptoms. To our knowledge this is the first report of GRGV in the UK. This suggests a broader distribution than previously reported and indicates the need for further surveillance of grapevine to establish current distribution. This work was funded under the Defra-Fera Long Term Service Agreement.