Mosaic Disease of Rhoeo discolor Caused by a Strain of Tobacco Mosaic Virus. S. M. Thompson, Former Graduate Student, Botany Department, University of Maryland, College Park 20742. M. K. Corbett, Professor, Botany Department, University of Maryland, College Park 20742. Plant Dis. 69:356-359. Accepted for publication 11 December 1984. Copyright 1985 The American Phytopathological Society. DOI: 10.1094/PD-69-356.

Rhoeo discolor plants showing mosaic symptoms were systemically infected with a rigid rod virus of the tobamovirus group. The virus was mechanically transmissible but had a limited host range. It did not infect Nicotiana tabacum ‘Turkish,’ N. glutinosa, Phaseolus vulgaris ‘Pinto,’ or Datura stramonium, all of which are susceptible to the type strain of tobacco mosaic virus (TMV). Properties of the virus in crude R. discolor sap were thermal inactivation between 92 and 94 C for 10 min, aging in vitro over 8 mo, and dilution end point between 10^–5 and 10^–6. Healthy plants of R. discolor inoculated with partially purified preparations of the virus developed a systemic mosaic 1–2 mo after inoculation. The virus gave precipitin zones of serological relatedness in reciprocal gel double-diffusion tests with type TMV.