TOBACCO MOSAIC-VIRUS SUBLIMINAL INFECTION OF AFRICAN VIOLET

'Wild White' African violet (Saintpaulia ionantha H. Wendl.) was previously reported to be probably immune to tobacco mosaic virus (TMV) infection. In this study, 15 other S. ionantha cultivars were mechanically inoculated with 200 mug TMV/ml sodium phosphate buffer. Two weeks postinoculation, tissue was harvested and assayed for TMV infection by a) TMV-specific enzyme-linked immunosorbent assay and b) bioassay on the local lesion host, 'Samsun NN' tobacco (Nicotiana tabacum L.). There was evidence of TMV infection in directly inoculated tissue of each of the 15 S. ionantha cultivars but not in noninoculated tissue or in mock-inoculated control plants. The small amount of virus recovered from inoculated tissue was shown to be the result of de facto viral infection and not the detection of residual inoculum. Postinoculation treatment with ultraviolet light significantly enhanced virus recovery in directly inoculated tissue. These results suggest that S. ionantha is not immune to TMV infection and that this host undergoes an asymptomatic subliminal infection by TMV.