PRUNUS CERASIFERA AS A HOST OF PLUM POX VIRUS IN BULGARIA
Four hundred twenty-five trees of myrobalan (Prunus cerasifera Ehrh.) growing along the roads and small areas within residential spaces, private gardens, and parks in Sofia and around the town were visually inspected for virus symptoms and tested for the presence of PPV by DAS-ELISA. DASI-ELISA for strain differentiation was carried out for the identification of PPV isolates, using PPV-M and PPV-D specific monoclonal antibodies. A small number PPV isolates was tested with M/D specific primers targeting two different regions: cylindrical inclusion protein (CIP) and the coat protein (CP) amino terminal. The primers targeting the 3’-terminal region of the CP gene allowed the detection of a few unknown PPV isolates. While the inspected trees showed highly variable leaf symptoms, only a small number of them showed symptoms on the fruits. The overall detection of PPV was 49%, PPV-M was found in the majority (57%) of the samples, followed by PPVD (29%). Mixed infections occurred in 2% of the samples, and the diseased trees affected by the unknown PPV strain were 12%. PPV-Rec strain was identified in one infected tree. For the first time in Bulgaria two ornamental species, P. cerasifera var. rubrum and P. cerasifera cv. Pissardii were found to be natural hosts of PPV. Strains M and D alone or in mixture were identified in the infected trees of these species. IC-RT-PCR results showed the presence of mix infection of PPV-M and PPV-Rec strains in one tree of Armeniaca desicarpa (P. cerasifera x P. armeniaca). The presence of PPV in cultivated and uncultivated, edible and ornamental P. cerasifera species provides strong evidence that they are natural PPV reservoirs in Bulgaria.