Tunisian Potato virus Y isolates with unnecessary pathogenicity towards pepper: support for the matching allele model in eIF4E resistance–potyvirus interactions

Abstract

The pathogenic properties of Potato virus Y (PVY; genus Potyvirus, family Potyviridae) isolates collected in naturally infected pepper (Capsicum annuum) fields in Tunisia were evaluated against recessive resistance alleles at the pvr2 locus of pepper. Two pathotypes were observed. Pathotype (0,1,3) isolates were able to infect plants carrying the susceptibility allele pvr2+, together with pvr21/pvr21 and pvr23/pvr23 plants, but not pvr22/pvr22 plants. Pathotype (0) isolates were only able to infect pvr2+/pvr2+ plants. On the other hand, sequence data and phylogenetic analyses revealed three major groups of isolates, each characterized by particular amino acid residues in the central part of the VPg, the pathogenicity factor towards pvr2. Correspondence between pathogenic properties and phylogeny suggested a single evolutionary step for pathogenicity towards the pvr21 and pvr23 resistances, possibly under the selective pressure of pvr21. Indeed, 23% of the pepper plants in this area were shown to carry the pvr21 resistance, while pvr23 was not detected. The data suggested that pathogenicity towards pvr21 and pvr23 were not costly for PVY to infect susceptible pepper genotypes and supported the matching allele model for pepper–PVY interactions.