First Report of Tobacco as a Natural Host of Tomato yellow leaf curl virus in Spain.

Two begomovirus species, Tomato yellow leaf curl Sardinia virus (TYLCSV) and Tomato yellow leaf curl virus (TYLCV), have been identified as causal agents of tomato yellow leaf curl disease (TYLCD) in Spain. TYLCSV was reported in Spain in 1992 and TYLCV in 1997 on tomato crops (3). TYLCV was also reported in common bean (Phaseolus vulgaris L.) and pepper (Capsicum annuum L.) crops in southern Spain in 1997 and 1999, respectively. During the summer of 2004, symptoms of yellowing, crumpling, and necrosis of new leaves were observed sporadically in young, field-grown tobacco (Nicotiana tabacum L.) plants in the Badajoz Province. These tobacco plants were next to tomato crops where TYLCV was detected for the first time in Badajoz in 2003. In September 2004, four symptomatic tobacco plants were selected for double antibody sandwich enzyme linked immunosorbent assay (DAS-ELISA) and polymerase chain reaction (PCR) identification analyses. Serological analyses were carried out in two repetitions and with the following polyclonal antisera: Potato virus Y (PVY) (Loewe Biochemica, Sauerlach, Germany); Tobacco mild green mosaic virus (produced in our laboratory); Tobacco mosaic virus (BIO-RAD, Marnes-La-Coquette, France); and Tomato spotted wilt virus (Loewe Biochemica). A simplified method of duplex PCR was used for a rapid, sensitive, and simultaneous detection of TYLCSV and TYLCV (2). Mixed infections of PVY and TYLCV were detected in all four tobacco samples tested. TYLCV infection was confirmed using the primer pair TY-1/TY-2 specific for the coat protein (CP) gene of begomoviruses (1). The CP fragment was digested with the restriction enzyme AvaII, and the pattern obtained corresponded to that obtained from TYLCV-infected tomato that served as a positive control. Two PCR products from different tobacco samples were sequenced and both showed 100% identity with the corresponding region (Almería) of TYLCV (GenBank Accession No. AJ489258) and 99% with TYLCV-Mild (Spain) (GenBank Accession No. AJ519441), confirming the diagnosis. The symptoms observed in the tobacco plants can not be attributed solely to TYLCV since the virus was present in a mixed infection with PVY. However, tobacco infected with TYLCV may serve as an important alternate host for TYLCV in the tomato cropping system. To our knowledge, this is the first report of N. tabacum as a natural host of TYLCV in Spain. References: (1) G. P. Accotto et al. Eur. J. Plant Pathol. 106:179, 2000. (2) P. Martínez-Culebras et al. Ann. Appl. Biol. 139:251, 2001. (3) J. Navas-Castillo et al. Plant Dis. 81:1461, 1997.