Eleven monoclonal antibodies specific to plum pox potyvirus (PPV) coat protein were obtained by hybridoma technology from Spanish PPV isolates. In addition, two monoclonal antibodies specific for PPV cylindrical inclusions (CIP non‐structural proteins) were obtained. The monoclonal antibodies specific for PPV coat protein were assayed by DASI ELISA against 81 PPV isolates. At least nine different epitopes were found and 21 distinct serological patterns of reaction (serogroups) were established using nine selected monoclonal antibodies against the collection of PPV isolates, indicating the high variability of coat protein among PPV isolates. Changes in epitope composition were observed after aphid and mechanical transmission, indicating the occurrence of mixtures of isolates in field trees. Monoclonal antibody 5B reacted with all PPV isolates assayed, with very high affinity, using DASI ELISA. This method was compared with immunocapture‐PCR on field samples in spring, and showed very good coincidence of results. The efficiency of PPV detection can be slightly increased using monoclonal antibodies specific to cylindrical inclusions mixed with monoclonal antibodies against structural proteins, and using mixtures of monoclonal antibodies against different epitopes of coat protein. ELISA‐I and immunoprinting‐ELISA were able to detect CIP and PPV in extracts and tissue section, respectively, of woody plants. Two monoclonal antibodies offer the possibility of distinguishing between Marcus and Dideron PPV types (M or D). These D‐specific monoclonal antibodies can be used in routine tests with high affinity.

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The characterization of pathogenic properties of two infectious clones of Plum pox virus (PPV) isolates, pGPPV (D group) and pGPPVPS (M group), was investigated in their woody hosts (seedlings of Prunus spp.). The two clones differed in their ability to infect plum and peach cultivars, from no infection to local and systemic infection. The phenotype determinants were located with a set of chimeric viruses from the two clones. In plum, determinants of systemic infection were located in a genomic fragment encoding the P3 and 6K1 proteins, which might influence genome amplification or virus movement. The capacity of pGPPVPS to induce stable local and systemic infections in peach was not located accurately and might be influenced by multiple determinants carried by different regions of the genome, excluding those encoding the protein 1, the majority of helper component, nuclear inclusions a and b, and coat protein. We conclude that PPV infections of plum and peach are governed by different determinants.