COMPETITIVENESS OF DIFFERENT PLUM POX VIRUS ISOLATES IN EXPERIMENTAL MIXED INFECTION REVEALS RATHER ISOLATE-THAN STRAIN-SPECIFIC BEHAVIOUR

Three major Plum pox virus (PPV) strains have been identified as prevalent in most of the central-and east-European countries, i.e. PPV-M, PPV-D and PPV-Rec. PPV-Rec, which arose from homologous recombination between PPV-M and PPV-D, has been recognised only recently. Although important studies on its genetic variability have been done in the last years, the biological and epidemiological data are scarce. It is generally thought that recombination events may provide some selective advantage to the recombinant isolate over its parent variants to become established in nature. Therefore, the behaviour of different PPV-Rec isolates in mixed infection with either PPV-M or PPV-D was studied by simultaneous co-inoculation of Nicotiana benthamiana plants. A stable balanced inter-strain mixed infection could be detected in about 40% of individual plants. No clear-cut strain-specific behaviour of PPV isolates in term of competitiveness in mixed infection could be observed. This further confirmed the existence of biological variability within single PPV strains.