Host Groups of Potato virus Y: Vanishing Barriers

Abstract

Potato virus Y (PVY) is one of the rare members of the genus Potyvirus for which the genetic diversity is structured by the plant species of origin. This structure has been explained by the occurrence in some crop species of barriers to infection by PVY isolates originating from other plant species. A particularly strong barrier to infection has been shown between PVY isolates from pepper (Capsicum spp.) and potato (Solanum tuberosum). PVY isolates from potato belong mainly to clades N and O and are poorly or not infectious at all in pepper. By contrast, PVY isolates from pepper belong mainly to clade C1 and are poorly or not infectious at all in potato. Recent surveys and genetic analyses, however, have revealed that PVY isolates of clades N and/or O can be quite frequent in pepper crops. Conversely, PVY isolates of clade C1 are almost absent in potato crops. However, we showed that PVY isolates of clade C1 from pepper are infectious in a potato cultivar devoid of the resistance gene Nc tbr . It has also been shown that, among pepper, tomato and tobacco genotypes carrying eIF4E-mediated recessive resistances, PVY evolution in one crop species could favour its future adaptation to other species. Altogether, these results suggest a lack of strong barriers to PVY host change between solanaceous crops. The contrast with older studies could be due to a range of factors, including an insufficient sampling effort in previous studies (too few isolates collected and characterised, too few plant genotypes assayed), to recent changes among PVY populations and/or to the contrasted behaviour of different genotypes within a plant species upon PVY inoculation.