Tobacco rattle virus. Coloured transmission electron micrograph (TEM) of virus particles (virions) of the tobacco rattle virus (TRV). This plant virus is a tobravirus, and has an RNA (ribonucleic acid) genome. It was first identified in 1931 in the tobacco plant (Nicotiana tabacum), one of the world's major cash crops. This virus also infects beet, bell pepper, spinach and potato plants. Symptoms are ringspots and tissue death. The virus is transmitted by several species of Trichodoridae nematode worms. Magnification: x125,000 when printed 10cm high.