Cowpea mosaic virus. Coloured transmission electron micrograph (TEM) of virus particles (virions) of the cowpea mosaic virus (CPMV). This plant virus is a comovirus, and has an RNA (ribonucleic acid) genome. It was first identified in 1959 in the cowpea plant (Vigna unguiculata), a plant cultivated as a fodder crop to feed livestock. This virus also infects several other legume plants. Symptoms are mosaic lesions and yellowing of the leaves. The virus is transmitted by several species of beetles. It is found in Cuba and eastern Africa. Magnification: x125,000 when printed 10cm high.