Cucumber mosaic virus. Coloured transmission electron micrograph (TEM) of virus particles (virions) of the cucumber mosaic virus (CMV). This plant virus is a cucumovirus, and has an RNA (ribonucleic acid) genome. It was first identified in 1934 in the cucumber plant (Cucumis sativus), a plant cultivated as a food crop. This virus also infects a wide range of other plants, including tomato and spinach plants. Symptoms are mosaic lesions and stunting and reduced fruit yield. The virus is transmitted by several species of aphids. Magnification: x125,000 when printed 10cm high.