Nepoviruses of the Americas

Abstract

The idea that plant viruses spread through the soil and infect healthy plants via the roots is nearly as old as the concept of viruses as causal agents of plant diseases. The first experimental proof that soil-inhabiting nematodes may serve as vectors of plant viruses was not obtained until 1958 when Hewitt et al. (51) published their significant findings linking soil transmission of grapevine fanleaf virus with the feeding of the ectoparasitic nematode Xiphinema index. This publication stimulated similar experiments on other soil-borne viruses, and by the early 1960s, several viruses with similar biological and physical properties were shown to have species of Xiphinema or Longidorus as vectors. In addition to grapevine fanleaf, the initial group of viruses with nematode vectors included tobacco ringspot, tomato ringspot, arabis mosaic, raspberry ringspot, strawberry latent ringspot, and tomato black ring. These viruses were indistinguishable morphologically and they were either serologically unrelated to each other or distantly related. Cadman (13) recognized that the viruses involved had close natural affinities and he proposed the group name NEPO viruses as a meaningful abbreviation of their two distinctive properties: nematode transmission and polyhedral-shaped particles. This group name has withstood the test of time, and although officially reduced to lower case letters, it now constitutes one of the 26 plant virus groups recognized by the International Committee on Taxonomy of Viruses (75).