Distribution of Plum pox virus in the Czech Republic

Plum pox virus (PPV) is widely distributed in plums and myrobalans in western, central and easternBohemia, in north-western, central and north-easternMoravia of theCzechRepublic. In southernBohemia and partly also in southernMoravia there is only a low and sporadic incidence. Naturally growing plums and myrobalans, and plums growing along roads were found to be the main sources and reservoirs of PPV infection. This high incidence in naturally growing plum and myrobalan trees makes it impossible to grow plum cultivars that are susceptible to PPV; only resistant cultivars can be grown in this country. In blackthorns the occurrence of PPV is limited to the regions with high and long-term presence of the virus. Therefore, we can conclude that blackthorn is not the primary, but a secondary source of PPV. On the other hand, sweet and sour cherries at localities of central and westernBohemia, and of southernMoravia are PPV-free. Till now the presence of strain PPV-C was not proved in theCzechRepublic. Strain PPV-M was proved only in two plum and one damson trees. It was also found in one apricot and one peach orchard planted with imported nursery material. Strain PPV-M appears to have been introduced recently and is absent from or has a very low incidence in spontaneous PPV hosts, while the widespread and long-term dissemination of strain PPV-D may indicate that it originated in the Czech Republic.