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First Report of Tomato torrado virus in Tomato Crops in France

In June 2008, tomato (Solanum lycopersicum L.) plants cv. Fer De Lance (De Ruiter Seeds, Bergschenhoek, the Netherlands) grown in greenhouses near Perpignan (southern France) showed growth reduction and necrotic lesions on fruits, stems, and basal parts of the leaves. Tomato torrado virus (ToTV) was suspected on the basis of symptoms and its recent description in Spain (4). Primer set A (3), designed to ToTV RNA-2, was used for reverse transcription (RT)-PCR experiments on RNA extracted from four infected plants and allowed the amplification of a 493-bp fragment. No amplification was observed from healthy plant extracts. The RT-PCR product was directly sequenced (GQ303330) and a BLAST search in GenBank revealed 99.8- and 99.5%-nt identity with Polish (EU563947) and Spanish type strain (DQ388880) isolates of ToTV, respectively. Double-antibody sandwich-ELISA tests were conducted on these four samples to check for the presence of other viruses commonly found in tomato crops in France. Tomato spotted wilt virus, Parietaria mottle virus, Cucumber mosaic virus, Tomato mosaic virus, and Potato virus Y were not detected but Pepino mosaic virus (PepMV) was detected in all samples. ToTV was mechanically transmitted to Physalis floridana but PepMV was not. This plant was used to inoculate healthy tomatoes that served as a ToTV source for further experiments. Mechanical inoculation to test plants showed that Nicotiana benthamiana, N. clevelandii, N. debneyi, N. glutinosa, Capsicum annuum, Solanum melongena, and some tomato cultivars (including Fer De Lance), in which typical necrotic symptoms were observed, were systemically infected by the virus. Isometric particles ~28 nm in diameter were observed by electron microscopy in crude extracts of infected plants negatively stained with 1% ammonium molybdate, pH 7. To confirm ToTV identification, whitefly transmission experiments were performed with Trialeurodes vaporariorum and Bemisia tabaci. Adult whiteflies were placed in cages with infected tomato plants for 1-, 24-, or 48-h acquisition access periods (AAP) before transferring them by groups of ~50 on susceptible tomato plantlets placed under small containers (six plants per AAP). Forty-eight hours later, plants were treated with an insecticide and transferred to an insect-proof containment growth room. Ten days later, RNA preparation from all plants was tested by RT-PCR for the presence of ToTV. No transmission was observed with a 1-h AAP. With a 24-h AAP, transmission to four of six test plants was observed with both whitefly species, while at 48 h, AAP transmission to three and four plants of six was observed with T. vaporariorum and B. tabaci, respectively. Noninoculated control plants were all negative by RT-PCR. These experiments confirm T. vaporariorum and B. tabaci as natural vectors of ToTV as previously described (1,2). ToTV has been already reported in Spain, Poland, Hungary, and Australia, but to our knowledge, this is the first report of ToTV in France. Our detection of ToTV in April 2009 from the same area revealed 7 positive tomato plants of 17 tested. This observation suggests the persistence of the disease in the Perpignan Region.

References: (1) K. Amari et al. Plant Dis. 92:1139, 2008. (2) H. Pospieszny et al. Plant Dis. 91:1364, 2007 (3) J. Van der Heuvel et al. Plant Virus Designated Tomato Torrado Virus. Online publication. World Intellectual Property Organization WO/2006/085749, 2006. (4) M. Verbeek et al. Arch. Virol. 152:881, 2007.