First Report of Grapevine Pinot gris virus (GPGV) in grapevine in France

Abstract

Grapevine Pinot gris virus (GPGV), belonging to the genus Trichovirus of the family Betaflexiviridae, was first identified by siRNA sequencing in northern Italy in 2012, in the grapevine varieties Pinot gris, Traminer, and Pinot Noir, which exhibited mottling and leaf deformation (1), and in asymptomatic vines, with a lower frequency. Since 2012, this virus has also been reported in South Korea, Slovenia, Greece (3), Czech Republic (2), Slovakia (2), and southern Italy (4). In 2014, GPGV was identified by Illumina sequencing of total RNAs extracted from leaves of the Merlot variety (Vitis vinifera) grafted onto Gravesac rootstock originated from a vineyard in the Bordeaux region of France. This Merlot plant exhibited fanleaf-like degeneration symptoms associated with Tomato black ring virus (TBRV) infection. Cuttings were collected in 2010 and maintained thereafter in a greenhouse. The full-length genome was assembled either de novo or by mapping of the Illumina reads on a reference GPGV genome (GenBank FR877530) using the CLC Genomics workbench software (CLC Bio, Qiagen, USA). The French GPGV isolate "Mer" (7,223 nucleotides, GenBank KM491305) is closely related to other European GPGV sequences; it exhibits 95.4% nucleotide identity with the reference Italian isolate (NC_015782) and 98 to 98.3% identity with Slovak isolates (KF134123 to KF134125). The higher divergence between French and Italian GPGV isolates was mainly due to differences in the 5' extremity of the genome, as already shown with the Slovak GPGV isolates. RNA extracted from phloem scrapings of 19 cv. Merlot vines from the same plot collected in 2014 were analyzed by RT-PCR using the specific primer pair Pg-Mer-F1 (5'-GGAGTTGCCTTCGTTTACGA-3') and Pg-Mer-R1 (5'-GTACTTGATTCGCCTC GCTCA-3'), designed on the basis of alignments of all available GPGV sequences from GenBank. The resulting amplicon of 770 bp corresponded to a fragment of the putative movement protein (MP) gene. Seven (35%) of the tested plants gave a strong positive amplification. Three RT-PCR products were directly sequenced and showed 99.3 to 99.5% identity within the MP gene of the GPGV-Mer isolate. Given the mixed viral infection status of the vines found infected by GPGV, it was not possible to associate a specific symptomatology with the presence of GPGV. Furthermore, similar RT-PCR tests were also performed on RNA extracts prepared from two plants of cv. Carignan that originated from a French grapevine collection, exhibiting fanleaf-like symptoms without any nepovirus detection. These samples similarly gave a strong positive amplification. The sequences obtained from the two Carignan vines showed 98.4 and 97.8% identity with the GPGV-Mer isolate. To our knowledge, this is the first report of GPGV in France. GPGV has been discovered in white and red berry cultivars, suggesting that its prevalence could be important in European vineyards (2). Further large-scale studies will be essential to determine the world prevalence of GPGV and to evaluate its potential effects on yield and on wine quality, as well as to shed light on GPGV epidemiology. Of particular concern is whether, like the other grapevine-infecting Trichovirus, Grapevine berry inner necrosis virus (GPGV) can be transmitted by the eryophid mite Colomerus vitis.