During 2001, watercress (Rorippa nasturtium-aquaticum) plants displayed in vegetable markets located in the district capital, Caracas, showed severe leaf distortion, chlorosis, and mosaic. Viral etiology was suspected, and several plants were brought to the lab for further analyses. Electron microscopic studies of leaf-dip preparations from symptomatic samples revealed flexuous viral particles 750 nm long. Infected cells contained pinwheel inclusions and scrolls typical of those associated with infection by a potyvirus. The virus was sap-transmitted back to watercress, which developed symptoms identical to those first observed. Disease symptoms were also reproduced on Nicotiana benthamiana using mechanical inoculation with watercress-infected sap. All samples were tested by enzyme-linked immunosorbent assay, using polyclonal antibodies (Agdia, Elkhart, IN) to Turnip mosaic virus (TuMV), the only potyvirus that has been found infecting watercress plants (1). TuMV was detected in 88% of 100 samples taken from 18 markets on a single day. Symptoms were noted in every market when visited once a month during a 6-month period. The high percentage of TuMV-infected watercress in the 18 local markets (all 10 to 11 km from watercress fields) makes further epidemiological studies desirable. To our knowledge, this is the first report of TuMV infection of watercress in Venezuela.
References: (1) A. Brunt et al. Viruses of Plants. CAB International, Wallingford, Oxon, UK. 1996.
