Biological and molecular characterization of two tomato strains of potato virus Y (PVY)

Two PVY tomato strains (LYE 84 and LYE 84.2), arising from the same natural isolate, and a strain originating from a wild Solanaceous host, Solanum nigrum (SON 41.2), were compared for host range and symptomatology. All strains induced mosaic without necrosis on tobacco as PVY^O strains. The two tomato strains behaved similarly on pepper, infecting only susceptible pepper cultivars (pathotype 0), whereas SON 41.2 was able to overcome the two alleles of the recessive resistance gene pvr2 (pathotype 1.2). On the other hand, only LYE 84.2 was virulent on tomato and broke the resistance of the wild genitor Lycopersicon hirsutum PI 247087. Sequence determination of the capsid gene and the 3′ non-coding region of LYE 84 and LYE 84.2 showed a total homology at both nucleic acid and amino acid levels. This suggests that LYE 84.2 has probably derived from LYE 84, that both strains have very similar sequences and that the capsid protein does not play a direct role in the resistance-breaking capacity of LYE 84.2.