RT-PCR EVIDENCE OF THE NON-TRANSMISSION THROUGH SEED OF PLUM POX VIRUS STRAINS D AND M

Abstract

Twelve different apricot selections and six peach varieties naturally infected with Plum pox virus (PPV) groups D and M, respectively, were used to investigate the role of seeds in the epidemiology of the virus. All plants were PPV-positive in IC-RT-PCR and the isolates were characterized by restriction analysis of amplicons with RsaI restriction and analysis of coat protein migration in 15% SDS-polyacrylamide gel, followed by Western blotting. The presence of PPV was checked on fully ripe seeds, germinating seeds and seedlings. One half of the apricot seed stock was analyzed by ELISA and IC-RT-PCR, separating cotyledons, also containing the embryo, from seed coats. The virus, in both species, was mainly localized in seed coats, but cotyledons were also infected. Seeds of the other half of the stock were germinated and maintained in an insect-proof screenhouse for over 3-years (apricot seedlings) or over 6 months (peach seedlings). Seedlings never showed symptoms and were found PPV-negative by molecular assays. The conclusion was that seeds have no role in PPV-M and PPV-D epidemiology.