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First Report of Tomato chlorosis virus Infecting Tomato Crops in Brazil

During 2006 and 2007 in the region of Sumaré, state of São Paulo, Brazil, surveys were done on tomato (Solanum lycopersicum L.) virus diseases in three open field-grown crops. The data revealed low incidence (0.25 to 3.42%) of randomly distributed plants exhibiting interveinal chlorosis and some necrosis on the basal leaves. Symptoms were only observed on old fruit-bearing plants. Preliminary analysis of thin sections of symptomatic leaves from one plant by transmission electron microscopy revealed the presence of aggregates of thin, flexible, and elongated particles in some phloem vessels, suggesting infection with a member of the genus Crinivirus, family Closteroviridae. Total RNA was extracted separately from leaves of 10 symptomatic plants and used for one-step reverse transcription (RT)-PCR using the HS-11/HS-12 primer pair, which amplifies a fragment of 587 bp from the highly conserved region of the heat shock protein (HSP-70) homolog gene reported for Tomato infectious chlorosis virus (TICV) and Tomato chlorosis virus (ToCV) (1). The RT-PCR product was subsequently tested by nested-PCR for single detection of TICV and ToCV using primer pairs TIC-3/TIC-4 and ToC-5/ToC-6, respectively (1). Only one fragment of approximately 463 bp was amplified from 7 of the 10 plants with the primer pair specific for ToCV. No amplification was obtained with the primers specific for TICV. Two amplicons of 463 bp were purified and directly sequenced in both directions. Sequence comparisons of the 463-bp consensus sequence (GenBank Accession No. EU868927) revealed 99% identity with the reported sequence of ToCV from the United States (GenBank Accession No. AY903448) (3). Virus-free adults of Bemisia tabaci biotype B confined on symptomatic tomato leaves for a 24-h acquisition access period were able to transmit the virus to healthy tomato plants, which reproduced the original symptoms on the bottom leaves 65 days after inoculation under greenhouse conditions. Infection from transmission was confirmed by RT-PCR using the HS-11/HS-12 primer pair. In addition to B. tabaci biotype B, the greenhouse whitefly, Trialeurodes vaporariorum, has also been reported as a vector of ToCV, although it is less efficient than the B. tabaci biotype B in transmission of this virus (4). T. vaporariorum, which was previously considered limited to greenhouses, was recently reported in tomato and green bean (Phaseolus vulgaris L.) crops under field conditions in São Paulo State (2). Therefore, it might also contribute to the spread of ToCV in tomato crops in São Paulo. To our knowledge, this is the first report of ToCV in Brazil and South America.

References: (1) C. I. Dovas et al. Plant Dis.86:1345, 2002. (2) A. L. Lourenção et al. Neotrop. Entomol. 37:89, 2008. (3) W. M. Wintermantel et al. Arch. Virol. 15:2287, 2005. (4) W. M. Wintermantel and G. C. Wisler. Plant Dis. 90:814, 2006.