First Report of Strawberry vein banding virus on Strawberry in Italy.

Abstract

In the summers of 2007 and 2008, diseased strawberry plants (Fragaria x ananassa Duch.) were observed in production fields in Ferrara and Forlì-Cesena districts (Emilia-Romagna Region) in northern Italy. Plants exhibited poor growth, leaf chlorosis, decline, and reduced fruit production. Older leaves sometimes displayed a premature purplish discoloration, while the younger leaves appeared chlorotic and were reduced in size with a marked yellow edge. Symptom severity was dependent on the cultivar and growing conditions. Sixty-one leaf samples were collected from diseased plants from production fields and cultivar collections. Each sample was tested by grafting on Fragaria vesca (clone 'UC4 and UC5') and F. virginiana (clone 'UC10' and 'UC11'). Forty-five days after indexing different symptoms, characteristic of viral diseases, appeared on indicator plants. In particular, 24 samples showed Strawberry vein banding virus (SVBV)-like symptoms with chlorotic streaks along and on both sides of the main leaf veins of UC5, UC10, and UC11 indicator plants. Molecular methods were also used to better investigate the causal agent. Nucleic acids were extracted from young leaves of field and indicator plants by the cetyltrimethylammoniumbromide method (1). PCR analyses were performed with primer pair SVBVdeta/SVBVdetb as previously described to specifically amplify a product of 423 bp (2). SVBV was detected on all symptomatic indicator plants and corresponding field samples as well as on the positive control sample (supplied by J. D. Postman, National Clonal Germplasm Repository, Corvallis, OR and I. E. Tzanetakis, Oregon State University, Corvallis). No amplicons were detected from nucleic acids extracted from symptomless strawberry plants. PCR products, amplified from four Italian SVBV isolates, were cloned and sequenced and represent part of ORF IV of the SVBV genome that codes for the coat protein (CP). Italian SVBV isolates were more similar to the U.S. isolates than to the Chinese isolates (Genbank Accession Nos. AY862389, AY955374, X97304, AY605662, AY605663, and AY605664), showing 93 and 86% nt sequence identity, respectively. Strawberry vein banding disease has been reported previously in Italy in 1986 (3), but to our knowledge, this is the first finding of SVBV on strawberry field plants in Italy. SVBV was listed as a quarantine pest by the European and Mediterranean Plant Protection Organization (OEPP/EPPO) in 1978, but its spread has been increasing within European countries. Further studies should be done to ensure that strawberry propagating material is free of known viruses including SVBV.