SEROLOGICAL AND MOLECULAR TYPING OF PLUM POX VIRUS ISOLATES IN THE NORTH OF ROMANIA
L. Zagrai, I. Zagrai, B. Ferencz, I. Gaboreanu, K. Kovacs, I. Petricele, O. Popescu, D. Pamfil, N. Capote
Plum pox virus (PPV) is considered as the most dangerous viral pathogen of stone fruits. Although PPV is widespread in Romania and causes serious yield losses, little is known about the variability of its isolates. To secure this information we investigated 43 PPV isolates collected from five different plum orchards in the North of Romania in the Bistrita plum-growing area. PPV strains were serologically tested by TAS-ELISA using PPV-D and PPV-M specific monoclonal antibodies. Molecular strain typing was done by IC-RT-PCR targeting three genomic regions corresponding to (Cter)CP, (Cter)NIb/(Nter)CP and CI. RFLP analysis was used to distinguish the two major strains, D and M based on a RsaI polymorphism located in (Cter)CP. All PCR products targeting (Cter)CP and 8 PCR products spanning the (Cter)NIb/(Nter)CP cistrons were sequenced. All PPV isolates typed as PPV-M by serological analysis and by molecular differentiation in the genomic region corresponding to (C-ter)CP were confirmed by nucleotide sequencing to be homologous to PPV recombinant (PPV-Rec) previously reported. All these recombinant isolates share the same recombination breakpoint and conserve the DAG motif, which is considered essential for aphid transmission. This genetic similarity confirms that PPV-Rec may represent an ancestral group with a common evolutionary origin. Overall results provided evidence for endemic distribution of PPV-Rec in plum trees grown in the North of Romania.