Introduction

The geminiviruses are infectious plant viruses belonging to the family Geminiviridae and having circular, single-stranded DNA genomes packaged within geminate particles. The genome organization and biological properties of geminiviruses allow them to be divided into four genera [1, 4, 5, 6]. Those that have a monopartite genome and are transmitted by leafhopper insect vectors to monocotyledonous plants are members of the genus Mastrevirus, of which Maize streak virus is the type species. The genus Curtovirus comprises viruses that have a monopartite genome and are transmitted by leafhoppers to dicotyledonous plants, with Beet curly top virus as the type species. The genus Topocuvirus has only one member (also the type species): Tomato pseudo-curly top virus, which has a monopartite genome and is transmitted by tree hoppers to dicotyledonous plants. The fourth genus, Begomovirus, includes viruses that are transmitted by whiteflies to dicotyledonous plants; Bean golden yellow mosaic virus is the type species. These viruses have bipartite genomes (A and B components), with some exceptions (e.g., Tomato yellow leaf curl virus, Cotton leaf curl virus, Tomato leaf curl virus …) for which no B component has been found.

Geminiviruses cause significant yield losses to many crop plants throughout the world [8]. Because of their economic importance and the relative ease with which their DNA genomes can be cloned, many geminiviruses are now being characterized. Yet, at present virologists have no definitive guidelines for naming geminiviruses. Traditionally, viruses are named according to host, symptoms produced, and/or geographical origin (e.g., Wheat dwarf virus and African cassava mosaic virus), but it is becoming increasingly difficult or even impossible to name new geminiviruses because different virus species often cause similar symptoms in the same crop (e.g., Tomato yellow leaf curl virus (TYLCV) from Thailand, TYLCV from Israel, and TYLCV from Sardinia…). Naming is especially difficult when different species infect the same crop in the same geographical region (e.g., the tomato leaf curl viruses in India). Moreover, many isolates are now being characterized within a given virus species, adding a level of complexity to the system. This complexity is compounded by the recent discovery of the high frequency of recombination between species of geminiviruses [7].

We present here a system for naming geminiviruses and provide a list of geminiviruses with suggested names. This paper does not provide guidelines for identifying geminivirus species or strains; this will be done elsewhere. Here we aim only to propose a nomenclature system that is simple and flexible enough to accommodate the current situation and future discoveries in the family Geminiviridae . It is the result of numerous discussions over the GeminiNet and of an evening workshop discussion at the International Workshop on Bemisia and Geminiviral Diseases, Puerto Rico, June 1998. The authors felt it was important to begin a new Millennium with a proposal for geminivirus nomenclature system available.