An Isolate of Tomato Ringspot Virus from Trifolium ambiguum. S. W. Scott, Department of Plant Pathology and Physiology, Clemson University, Sandhill Research and Education Center, Columbia, SC 29224-3205. O. W. Barnett, Department of Plant Pathology and Physiology, Clemson University, Clemson, SC 29634-0377. Plant Dis. 75:73-77. Accepted for publication 4 July 1990. Copyright 1991 The American Phytopathological Society. DOI: 10.1094/PD-75-0073.

A Trifolium ambiguum plant growing in a field plot displayed a faint mottle typical of symptoms of virus infection in forage legumes. Sap inoculation to a series of herbaceous test plants indicated the presence of a virus. Preparations of crude sap examined in an electron microscope showed the presence of isometric particles. The virus was partially characterized and was identified as tomato ringspot virus (TomRSV) by gel double-diffusion serological tests. T. ambiguum has been proposed as a source of resistance to the common legume viruses. Although susceptibility of this species to TomRSV does not compromise the potential of some populations of T. ambiguum to be a source of resistance to other common legume viruses by means of interspecific crosses, the possibility of introducing susceptibility to TomRSV should be recognized.