Biological and molecular characterization of Potato yellow blotch virus,a new species of the genus Potyvirus

A new species of the genus Potyvirus infecting potatoes, with the proposed name Potato yellow blotch virus (PYBV), was discovered in a breeding line 99m-022-026 in Scotland. The infected plants show isolated yellow blotches on the leaves. The genome of PYBV contains a large open reading frame encoding a single polyprotein of 3054 amino acids. Sequence analysis shows that PYBV is closely related to Potato virus A (PVA), with an overall 72% identity at the nucleotide level for the whole genome. The least conserved P1 protease gene shares only 50% nucleotide identity with PVA. The host range of PYBV was comparable to PVA on solanaceaous and non-solanaceous indicator plant species with the exception of Solanum demissum A and Y. Different symptoms were also observed for PYBV and PVA in Nicotiana benthamiana, Nicotiana hesperis and Nicotiana occidentalis P1. The susceptibility of potato (Solanum tuberosum) cultivars to PYBV and PVA was similar. In over 5 years of investigation, PYBV has not been found in commercial seed and ware potato crops in Scotland.