Molecular and pathological characterization of N:O isolates of the Potato virus Y from Manitoba, Canada

Previous studies have identified a recombinant isolate group of the Potato virus Y (PVY), PVYN:O, which exhibits a PVYO serotype and a PVYN pathotype. Molecular fingerprinting indicated that the isolates possess a European (Eu)-PVYN/NTN-like P1 gene and one PVYN-PVYO recombinant joint at the HC/Pro-P3 site. In this study, the complete genomic RNA sequence of two isolates of PVYN:O was determined. The overall identities at the polyprotein level between PVYN:O and other isolates ranged from 94.1% to 97.2%. However, the identities varied from 70.9% to 100% when individual mature proteins were compared. Scanning the nucleotide sequences revealed that PVYN:O comprises a recombinant genome in which the segment of nucleotides I to similar to2400 is from Eu-PVYN, and the remainder from PVYO. Analysis of a population of PVYN:O isolates indicated the existence of pathological variants that induced different symptoms level in tobacco plants: severe, 16.7%; intermediate, 66.7%; and mild, 16.7%. Three representative isolates were selected for further analysis. Although pathologically different, the isolates were indistinguishable serotypically and genotypically when profiled using enzyme-linked immunosorbent assays and reverse transcription polymerase chain reaction, respectively. No significant differences in nucleotide sequence were observed among the three isolates in 5'-UTR-P1-HC/Pro as well as the CP-3'-UTR region.