Introduction

Abstract

At least 37 viruses naturally infect cultivated potatoes (e.g., Beemster and de Bokx, 1987; Salazar.1996; Jeffries, 1998); their natural modes of transmission, taxonomic status and accepted sigla are indicated in Table 5.1. Some of these viruses, notably Potato leafroll virus (PLRV), Potato aucuba mosaic virus (PAMV), Potato mop-top virus (PMTV), Potato virus A (PVA), Potato virus M (PVM), Potato virus S (PVS), Potato virus X (PVX) and Potato virus Y (PVY) occur worldwide in potato crops; others such as Arracacha virus B (AVB), Beet curly top virus (BCTV), Eggplant mottled dwarf virus (EMDV), Potato black ringspot virus (PBRV), Potato virus U (PVU) and Potato T virus (PVT) are important only in some geographical areas, and some such as Alfalfa mosaic virus (AlfMV), Cucumber mosaic virus (CMV), Sowbane mosaic virus (SMV), Tobacco necrosis virus (TNV) and Tobacco streak viruses (TSV) occur only rarely and sporadically in restricted geographical areas. Some of the latter, however, if they became more widespread would undoubtedly of greater importance. Although most of the viruses have long been known to infect potatoes, a few including Potato latent virus (PLV), Potato rough dwarf virus (PRDV), Potato yellowing virus (PYV) and Potato yellow vein virus (PYVV) have been recognised only during the past decade or so.