SOUR CHERRY STRAIN OF PLUM POX POTYVIRUS (PPV) - MOLECULAR AND SEROLOGICAL EVIDENCE FOR A NEW SUBGROUP OF PPV STRAINS

Properties of the unusual sour cherry strain of plum pox potyvirus (PP V-SoC) were investigated by sequencing its 3'-terminal 1,360 nt and ex amining its serological reactivity with several monoclonal antibodies (MAbs) to PPV. A significantly low degree of identity of the sequenced region has been found between PPV-SoC and other isolates of PPV. This is due to the high nucleotide divergence between the 5'-terminal regi on of the coat protein (CP) coding region of PPV-SoC and that of other isolates. Most nucleotide substitutions in the sequenced region are n ot silent and result in amino acid changes, especially near the N term inus of the CP. The unique 5' terminus of the PPV-SoC CP coding sequen ce has been utilized to develop a cRNA probe that hybridizes to PPV-So C but not to other isolates/members of the D or M subgroups of PPV. Th e N-terminal region of the PPV-SoC CP contains the recognizable DAG mo tif that determines aphid transmissibility of potyviruses. Aphid trans mission of PPV-SoC to herbaceous and woody hosts has been confirmed ex perimentally. Serological reactivity of PPV-SoC with 10 MAbs of PPV su ggest that PPV-SoC represents a new serotype of PPV that does not fall into the conventional D or M serotypes/subgroups. We propose that PPV -SoC represents a new subgroup of PPV strains, termed PPV-cherry (PPV- C), and that PPV-SoC is its prototype member.