CHARACTERIZATION OF THE SOUR CHERRY STRAIN OF PLUM POX VIRUS

Properties of the sour cherry isolate of plum pox virus (PPV) were inv estigated by reverse transcription-polymerase chain reaction (RT-PCR), restriction fragment length polymorphism (RFLP), molecular hybridizat ion, nucleotide sequencing, ultrathin sectioning of infected tissue, a nd graft transmission to different cherry rootstocks. Analysis of RT-P CR-amplified cDNA product from infected tissue with primers for the 3' noncoding region (3'-NCR) of the PPV genome and molecular hybridizati on of the amplified product with a labeled PPV cRNA probe verified tha t the potyvirus infecting sour cherry trees (Prunus cerasus) in Moldov a is an isolate of PPV. RFLP analysis of RT-PCR products from infected tissue with specific primers for the 3'-terminal region of the PPV co at protein (CP) gene revealed that the sour cherry isolate of PPV is a unique strain of PPV and a prototype of a new group that contains nei ther the RsaI nor the AluI restriction site. These results were confir med by nucleotide sequencing analysis. Nucleotide sequencing of the S' -NCR and the region coding for the 3'-terminal fragment of the PPV CP gene showed about 93% identity to that of other PPV isolates. RT-PCR a ssays of tissue extracts from three sour cherry cultivars demonstrated that sour cherry PPV was distributed systemically in sour cherry tree s and infected leaf, bark, root, flower, fruit, and seed tissues. The virus was successfully transmitted by chip bud grafting to rootstocks of P. avium (sweet cherry) and P. mahaleb.