PURIFICATION AND SEROLOGICAL CHARACTERIZATION OF A TOBACCO STREAK VIRUS ISOLATE INFECTING FIELD-GROWN ESCAROLE AND LETTUCE

Quasi-spherical particles approximately 27 nm in diameter were purified from plant tissue affected with escarole necrosis and the viruslike particles tentatively named escarole necrosis virus (ENV). Field-infected escarole and lettuce leaves developed chlorotic spots, which soon became necrotic, with the lesions coalescing to cover the leaf surface. Necrotic lesions formed on mechanically inoculated leaves, petioles, pulvini, and stems of Phaseolus vulgaris cv. Bountiful. A polyclonal antiserum was produced to ENV purified from infected Nicotiana tabacum. Results from immunoblots and one-dimensional peptide mapping using V8 protease and endoproteinase Lys-C indicated a close relationship between ENV and several tobacco streak virus (TSV) strains. The ENV virion has a 29.6 kDa protein capsid subunit and a tripartite genome of M(r) 3.97, 3.00, and 2.23 kb with a 0.687 kb subgenomic RNA. The ENV was identified as a TSV isolate. This is the first report of TSV field infection in escarole and lettuce.