Flue-cured tobacco is an economically important crop in Georgia. During the 1999 growing season, tobacco plants showing various degrees of mottling (mild to severe), mosaic, and vein clearing were observed in most counties in Georgia. In most cases, symptoms were not clearly those associated with Potato Y potyvirus (PVY) or Tobacco mosaic tobamovirus (TMV). The incidence of symptomatic plants in individual fields ranged from 0 to 90%. A survey was conducted in several tobacco-growing counties to ascertain the causal agent(s) of the disease. Symptomatic plants were collected from 11 counties: Appling, Atkinson, Bacon, Berrien, Coffee, Colquitt, Echols, Grady, Lowndes, Tattnall, and Ware. Leaf samples were tested by enzyme-linked immunosorbent assay (ELISA) for Cucumber mosaic cucumovirus (CMV), PVY, TMV, Tobacco etch potyvirus (TEV) and Tobacco vein mottling potyvirus. On the basis of ELISA, TMV and PVY were the most prevalent viruses, followed by CMV. From a total of 50 samples tested, 28 were doubly infected with TMV and PVY, 3 were positive for only TMV, and 5 were positive for only PVY. Eight samples were infected only with CMV, and one sample was doubly infected with PVY and TEV. The causal agent(s) in the remaining five samples could not be determined. Although PVY, TMV, TEV, and CMV occur to some degree every year, they have not been economically important in the past few years. It is interesting that the recent epidemic on tobacco and pepper in northern Florida was associated with CMV (1). Considering the predominance of double infections observed, diagnosis of virus-like symptoms in tobacco may require use of ELISA or other specific detection methods.
Reference: (1) T. A. Kucharek et al. Plant Dis. 82:1172, 1998.
