First Report of Arabis mosaic virus on Grapevine in Spain.

Arabis mosaic virus (ArMV; genus Nepovirus, family Comoviridae) is one of several nepoviruses responsible for infectious degeneration disease of grapevines in Europe (3). The first occurrence in Spain, in the summer of 2007, was found in Val de Salnés, Rias Baixas appellation, Galice on 25-year-old vines of the Albariño variety grafted onto an unidentified rootstock and showing leaf yellowing. The second finding was in the spring of 2008 in Barriobusto, Rioja appellation, Basque Country on 30-year-old vines of Tempranillo variety grafted onto 41B rootstock. In this case, no obvious foliar symptoms were observed but fruit set was very poor. Positive ELISA results were obtained at two different laboratories using antibodies to ArMV obtained from two companies (BIOREBA, Reinach, Switzerland and Sediag, Longvic, France). At a third lab, the presence of ArMV was further confirmed by reverse transcription (RT)-nested PCR using the primers described by Bertolini et al. (1). External primers ArMV 1 and ArMV 2 amplified a fragment of 340 bp from the coat protein region of the virus and internal primers ArMV i1 and ArMV i2 amplified a fragment of 203 bp. The specificity of the amplicons was subsequently confirmed by sequencing and comparison with other ArMV isolates available in the GenBank, EMBL, and DDBJ databases. Alignment performed using Blastn showed 85% nucleotide sequence identity with ArMV isolate NW (Accession No. AY017339). ELISA revealed co-infection with GLRaV-1 in Galice, GLRaV-3 in Rioja, and GFkV at both sites; these other viruses being common in their respective appellations. ArMV could be mechanically transmitted from rooted cuttings onto Chenopodium amaranticolor with an average of a 46% success rate (1:10 tissue/buffer ratio; [2]), but the range was very wide (0 to 100%) and dependent on the individual source vine. No statistical differences were found between nicotine or phosphate buffer for extraction or when using shoot tips or root tips as a source of virus (Fisher's exact test). Infection in C. amaranticolor was symptomless, but detectable by ELISA, and systemic. The Galician grapevine was an isolated plant, replanted on the spot of a dead one. Xiphinema diversicaudatum, the nematode vector of ArMV, was found in the vineyard soil. Only two ArMV-positive vines were found among 1,993 plants analyzed in Galice from 2005 to 2007 (no field data available for the second finding). In Rioja, one positive vine was found in a random sample of 74 vines from two different vineyards. Further testing of the neighboring vines indicated that one of the adjacent plants was also infected. This minimal spread since the vineyard was planted is suggestive of a lack of vectored transmission. In Spain as a whole, the virus seems to be rare and associated with the Atlantic biogeographic region. Both vineyards were planted before certified material became widely available. Currently, statutory testing of grapevine propagation material should prevent further spread. References: (1) E. Bertolini et al. Phytopathology 93:286, 2003. (2) G. P. Martelli, ed. Graft-Transmissible Diseases of Grapevines. Handbook for Detection and Diagnosis, FAO, Rome, 1993. (3) G. P. Martelli and E. Boudon-Padieu. Directory of Infectious Diseases of Grapevines and Viruses and Virus-like Diseases of the Grapevine. Bibliographic Report 1998-2004, CIHEAM, Paris, 2006.