Serological and Molecular Typing of Plum pox Virus Isolates in Moldavia, Romania

Abstract

Sharka, caused by Plum pox virus (PPV) is considered the most detrimental disease of plum. Although PPV is widespread in all plum growing areas from Romania and causes serious yield losses, limited information about the occurrence of PPV strains are available in some regions like Moldavia plum area. To supplement this information, fifty PPV isolates collected from five different commercial plum orchards from Moldavia were investigated. PPV detection was made by DAS-ELISA and by IC-RT-PCR. PPV strains were serologically determined by TAS-ELISA using PPV-D and PPV-M specific monoclonal antibodies. Molecular strain typing was done by RT-PCR targeting three genomic regions corresponding to (Cter)CP, (Cter)NIb/(Nter)CP and CI. RFLP analysis at the C-ter of CP cistron was used to distinguish the two major strains, D and M based on a RsaI polymorphism located in this genomic section. All PCR products targeting (Cter)CP and one PCR product spanning the (Cter)NIb/(Nter)CP 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 proved to be PPV recombinant (PPV-Rec) when the molecular analysis were performed in the region corresponding to NIb/CP. The sequencing results confirmed a high similarity with different sequences of PPV-Rec previously reported. Overall results provided that in Moldavia the predominant strain is PPV-D, followed with a much lower frequency by PPV-Rec which shares the CP gene with M strain. The mixed infections (PPV-D+PPV-Rec), were sporadically recorded in this plum growing area.