Characterisation of Potato virus Y nnp strain inducing veinal necrosis in pepper:: a naturally occurring recombinant strain of PVY

The full-length genome of Potato virus Y (PVY) nnp strain, recovered from pepper showing veinal necrosis of leaves, was cloned and sequenced, finding an organisation typical for PVY species. It consists of 9699 nucleotides (nt) excluding the 3' terminal poly( A) tail and contains an open reading frame of 9186 nt, encoding the putative polyprotein of 3061 amino acids. In ELISA, the isolate reacted with a monoclonal antibody specific for PVYC but not with antibodies against PVYN or PVYO. Sequence analysis strongly suggests that PVY-nnp originated from a recombination event involving a virus of the PVYO type and another parental virus, maybe resembling the PVYNP isolates, given the reasonably high similarity shared by PVY-nnp and Lye84.2 and Son41 isolates. The recombination event involved a breakpoint near the middle of the P1 gene, around position 603 of the viral genome. Proof for the existence of such a recombination comes from several lines of evidence, including similarity analysis, recombination analysis using six different methods and the different locations of nnp within phylogenetic trees constructed from genomic regions on either side of the identified recombination breakpoint.