A natural population of recombinant Plum pox virus is viable and competitive under field conditions

The isolate BOR-3, collected in Slovakia in 1996, was recently identified as a natural recombinant between an M and D type of Plum pox virus (PPV). Biological assays demonstrated its capacity to be aphid-and graft-transmitted to various Prunus spp. hosts. A study was carried out to determine the further presence of PPV recombinants in two epidemiologically distinct areas - Slovakia and France. Tools based on PPV-M and D subgroup typing, targeting P3-6K(1), CI and CP regions of the PPV genome were used for recombinant identification. Closely related recombinant variants were detected in different Prunus spp. during a survey conducted in Slovakia in 2001, but not within a set of selected PPV isolates from France collected between 1985 and 2001. Sequence analysis of the (Cter) NIb-(Nter) CP region of 10 recombinant isolates from Slovakia showed their high homology, reaching more than 98%. All the recombinant isolates shared the same recombination breakpoint situated in the C terminus of the NIb gene. Our study demonstrates that the PPV recombinants are viable and competitive with conventional PPV-M and D isolates. The present work indicates that the occurrence of recombinants within PPV isolates might be more common than previously assumed.