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First Report of Tobacco streak virus in Strawberry in the Eastern United States

In a 1998 virus survey (2) conducted on 23 commercial strawberry (Fragaria × ananassa Duchesne) production farms in the state of Maryland, leaf samples from 1,100 randomly sampled plants were sent to the U.S. Department of Agriculture laboratory in Corvallis, OR, for testing by enzyme-linked immunosorbant assays (ELISA). The viruses identified were Strawberry mild yellow edge, Strawberry crinkle, Strawberry veinbanding, Strawberry mottle, and Tomato ringspot viruses, all of which are known in the eastern United States. Tobacco streak virus (TSV) also was identified in 17 of the samples: 12 originated from a 1-year-old planting of ‘Sweet Charlie’ and 5 from another farm, of which 4 were from a 2-year-old ‘Sweet Charlie’ planting and 1 was from a 2-year-old ‘Delmarvel’ planting. Triple antibody sandwich ELISA was used to detect TSV following the procedures described by Finn and Martin (1), except that leaves from test plants were homogenized (1:20, wt/vol, in blocking buffer) and flat bottom microtiter plates (Nunc, Roskilde, Denmark) and goat anti-mouse (polyvalent) alkaline phosphatase conjugate were used in the assays. The absorbance of each well at 405 nm (A₄₀₅) was read in an ELISA plate reader. Reactions were considered positive if the A₄₀₅ values were greater than five times the values of healthy samples. The A₄₀₅ values of healthy samples ranged from 0.0 to 0.04, with values greater than 0.20 considered positive for TSV. An independent determination of TSV was made in plants shipped from Florida to Maryland in 1999. In this instance, leaf samples from ‘Sweet Charlie’ plants were sent by the Maryland Department of Agriculture to Agdia Inc. (Elkhart, IN), where samples tested positive for TSV.

References: (1) C. E. Finn and R. R. Martin. Plant Dis. 80:769, 1996. (2) S. C. Hokanson, et al. Adv. Strawberry Res. In press.