During the spring and summer of 2010, a survey for viruses was conducted in two tobacco field trials at the Agricultural Research and Experimentation Council in Scafati, Campania, Italy. A total of 1,392 symptomatic and asymptomatic tobacco plants (cv. Burley) were sampled, and leaves were analyzed by double-antibody sandwich-ELISA using polyclonal antisera against five tobacco-infecting viruses: Tobacco mosaic virus, Potato virus Y, Cucumber mosaic virus, Alfalfa mosaic virus, and Tomato spotted wilt virus (TSWV) (Loewe, Munich, Germany). Only one plant was positive to TSWV. Symptoms on this plant were severe necroses on the stem with a few chlorotic/necrotic leaflets on the top of the plant. This result was subsequently confirmed by reverse transcription (RT)-PCR. The primers (5′-ATGTCTAAGGTTAAGCTC-3′ forward and 5′-TTAAGCAAGTTCTGTGAG-3′ reverse) targeted the nucleocapsid gene of TSWV and amplified the expected product of approximately 800 bp (2). The resultant sequence (GenBank Accession No. JF290419) was aligned and edited using BlastN, displaying 99.9% identity with deposited TSWV nucleocapsid gene sequences in GenBank, with no similarity to any other targets, which confirmed the presence of TSWV in tobacco. Leaf homogenate from the tobacco symptomatic plants was inoculated onto three plants of Nicotiana benthamiana, N. glutinosa, and Datura metel. All plants developed a systemic necrosis after 7 days. Inoculation from N. glutinosa back to cv. White Burley tobacco produced symptoms similar to those observed in the field. Two plants from each species were used as noninoculated controls, which remained asymptomatic. TSWV infection has been responsible for severe epidemics on tobacco throughout the United States and Greece, with losses estimated as much as 85% (1,3). The presence of TSWV in Italy could therefore represent a serious threat for tobacco in the region, especially considering that it is prevalent in other crops in the area and vectors are widespread.
References: (1) E. K. Chatzivassiliou. Plant Dis. 92:1012, 2008. (2) R. K. Jain et al. Plant Dis. 82:900, 1998. (3) B. Mandal et al. Ann. Appl. Biol. 151:67, 2007.
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