D. L. Trudgill

Nepoviruses: Transmission by Nematodes

Nepoviruses share many biological and molecular characteristics such as symptom types, extensive host ranges, transmissibility through seed, isometric 28-nm-diameter particles, bipartite single-stranded RNA (ssRNA) genomes, and a single coat protein species of about 60 kDa. Some nepoviruses are transmitted by longidorid nematodes, a property that is reflected in the name nepovirus, which stems from nematode-transmitted viruses with polyhedral particles. However, this property has been established only for about one third of the viruses currently classified as nepoviruses (Murant, 1989), and for many others the mode of transmission is unknown. Many nepoviruses, including most of those transmitted by nematodes, have been shown to be transmitted through seed and pollen (Murant, 1983). Those nepoviruses known to have nematodes as vectors are transmitted by species of Longidorus or Xiphinema (Brown, 1989) or, in one instance, Paralongidorus (Jones et al., 1994). Only for tobacco ringspot virus (TRSV) have other animals (several species of arthropod) been implicated as natural vectors (Dunleavy, 1957; Komuro and Iwaki, 1968; Messieha, 1969; Rani et al., 1969; Schuster, 1963).