Parsnip yellow fleck virus. Coloured transmission electron micrograph (TEM) of virus particles (virions) of the parsnip yellow fleck virus (PYFV). This plant virus is a sequivirus, and has an RNA (ribonucleic acid) genome. It was first identified in 1968 in the parsnip plant (Pastinaca sativa), a plant cultivated as a food crop. This virus also infects several other plants, including celery and chervil. Symptoms are yellow flecks and mosaic lesions forming on the leaves. The virus is transmitted by Cavariella species of aphids. It is found in Germany and the UK. Magnification: x125,000 when printed 10cm high.