First Report of Tomato torrado virus Infecting Tomato in Single and Mixed Infections with Cucumber mosaic virus in Panama
Authors: Herrera-Vásquez J. A. , Alfaro-Fernández A. , Córdoba-Sellés M. C. , Cebrián M. C. , Font M. I. , Jordá C. 
Published: January 2009

In February of 2008, in open-field-grown tomato crops (Solanum lycopersicum L.) from the central regions of Coclé, Herrera, Los Santos, and Veraguas of Panama, unusual disease symptoms, including deformation, necrosis, purple margins, interveinal yellowing, downward and upward curling of the leaflets alternately, necrotic lines in sepals and branches, fruits distorted with necrotic lines on the surface, and severe stunting, were observed. Tomato production was seriously damaged. To verify the identity of the disease, five symptomatic tomato plants from four fields of these regions were selected and analyzed by double-antibody sandwich (DAS)-ELISA using specific antibodies to Cucumber mosaic virus (CMV), Potato virus X (PVX), Potato virus Y (PVY), Tomato mosaic virus (ToMV), Tomato spotted wilt virus (TSWV) (Loewe Biochemica, Sauerlach, Germany), and Pepino mosaic virus (PepMV) (DSMZ, Braunschweig, Germany). Total RNA was extracted from all plants and tested using reverse transcription (RT)-PCR with three pairs of specific primers: one pair designed to amplify 586 bp of the coat protein gene of CMV (CMV-F 5′-CCTCCGCGGATGCTAACTT-3′ and CMV-R 5′-CGGAATCAGACTGGGAGCA-3′) and the other two pairs to Tomato torrado virus (ToTV) that amplify 580 and 574 bp of the polyprotein (4) and coat protein (Vp23) (3) region of RNA2, respectively; and by dot-blot hybridization with a digoxygenin-labeled RNA probe complementary to the aforementioned polyprotein. The serological analysis for PVX, PVY, ToMV, TSWV, and PepMV were negative. ToTV was detected in all samples analyzed. Three of these samples were also positive for CMV by serological and molecular analysis. No differences in symptom expression were observed between plants infected with both viruses or with ToTV alone. RT-PCR products were purified and directly sequenced. BLAST analysis of one CMV sequence (GenBank Accession No. EU934036) showed 98% identity with a CMV sequence from Brazil (most closely related sequence) (GenBank Accession No. AY380812) and 97% with the Fny isolate (CMV subgroup I) (GenBank Accession No. U20668). Two ToTV sequences were obtained (GenBank Accession Nos. EU934037 and FJ357161) and showed 99% and 98% identities with the polyprotein and coat protein region of ToTV from Spain (GenBank Accession No. DQ388880), respectively. CMV is transmitted by aphids and is distributed worldwide with a wide host range (2), while ToTV is transmitted by whiteflies and has only been reported in tomato crops in Spain and Poland and recently on weeds in Spain (1). To our knowledge, this is the first time ToTV has been detected in Panama and the first report of CMV/ToTV mixed infection.

References: (1) A. Alfaro-Fernández et al. Plant Dis. 92:831, 2008. (2) A. A. Brunt et al. Plant Viruses Online: Descriptions and Lists from the VIDE Database. Online Publication, 1996. (3) H. Pospieszny et al. Plant Dis. 91:1364, 2007. (4) M. Verbeek et al. Arch. Virol. 152:881, 2007.