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

摘要

The pathogenicity properties of Potato virus Y (PVY; genus Potyvirus, family Potyviridae) isolatescollected in naturally-infected pepper (Capsicum annuum) fields in Tunisia were evaluated againstrecessive 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 withpvr21/pvr21 and pvr23/pvr23 plants but not pvr22/pvr22 plants. Pathotype (0) isolates were only ableto infect pvr2+/pvr2+plants. On the other hand, sequence data and phylogenetic analyses revealedthree major groups of isolates, each characterized by particular amino acid residues in the centralpart of the VPg, the pathogenicity factor towards pvr2. Correspondence between pathogenicityproperties and phylogeny suggested a single evolution step for pathogenicity towards the pvr21 andpvr23 resistances, possibly under the selective pressure of pvr21. Indeed, 23% of the pepper plantsin this area were shown to carry the pvr21 resistance while pvr23 was not detected. The datasuggested that pathogenicity towards pvr21 and pvr23 were not costly for PVY to infect susceptiblepepper genotypes and supported the matching allele model for pepper-PVY interactions.