Tobacco veinal necrosis determinants are unlikely to be located within the 5′ and 3′ terminal sequences of the potato virus Y genome

Summary

Three potato virus Y isolates, representatives of distinct PVY groups, identified in potato fields in northern Poland were submitted to biological and molecular analysis. Phenotypically, two isolates, PVY^N-Ny and PVY^N-Wi, belong to the necrotic strain and the third one (PVY^O-LW) to the common strain. PVY^N-Wi, however, did not react with monoclonal antibodies directed against the necrotic strain isolates which recognise PVY^N-Ny. To characterise the isolates, coat protein genes were sequenced and compared with sequences from databases. The necrotic PVY^N-Wi isolate showed 99% amino acid homology with the common one–PVY^O-LW and significantly differed from the second necrotic isolate (PVY^N-Ny). Sequence based homology matrix and phylogenetic analysis lead to classification of PVY^N-Ny into group I, encompassing solely necrotic strain isolates, whereas PVY^N-Wi falls into a phenotypically heterogeneous group II. The sequence analysis allowed for identification of putative group I–specific epitopes. 3′NTR (non-translated region) sequences were identical for PVY^N-Wi and PVY^O-LW. The 5′NTR, P1 gene, coat protein gene and 3′NTR sequences of the common (PVY^O-LW) and the necrotic (PVY^N-Wi) isolates are 99–100% homologous. This suggests that tobacco veinal necrosis determinants are located outside the 3′ and 5′ terminal sequences of the PVY genome.