Biological behavior and partial molecular characterization of six Chilean isolates of Plum pox virus

Plum pox virus (PPV) strain D was first detected in Chile in 1992 infecting Prunus trees including peaches, nectarines, apricots, and plums. Since then, quarantine efforts have included periodic surveys in the central zone of the country, the main region for stone fruit production. This work describes the characterization of six PPV isolates from this area of Chile, using biological and molecular approaches. PPV isolates were introduced into Prunus tomentosa and Nicotiana benthamiana hosts by grafting and mechanical inoculation, respectively. Symptoms were evaluated by following the appearance of circular necrotic spots and mosaic in leaves of P. tomentosa and mosaic and some-leaf deformation in N. benthamiana. Molecular analysis was carried out using reverse transcription-polymerase chain reaction, allowing the cloning and sequencing of 1.34-kb fragments corresponding to the 3' region of the replicase gene, the complete coat protein (CP) gene, and the 3' nontranslated region of the PPV genome. Evolutionary distance analysis of these nucleotide sequences and their deduced coat protein amino acid sequences grouped the six Chilean isolates among strain D isolates, with closest genetic distances to those of Central Germany and Poland. Representative sources of these isolates suggest that strain D could be the only type of PPV currently present in Chile.