Prunus host range of Plum pox virus (PPV) in the United States by aphid and graft inoculation

Plum pox (Sharka) is a serious virus disease of stone fruits caused by the Plum pox virus (PPV). To determine which species could function as potential hosts and virus reservoirs, we used aphid transmission and bud or chip grafting to evaluate the susceptibility of commercial, ornamental, and wild Prunus species to isolates of PPV found in Pennsylvania, USA. Following inoculation, test trees were observed for symptoms, analyzed by enzyme-linked immunosorbent assay (ELISA) and polymerase chain reaction (PCR), back-assayed to healthy peach, and followed through at least four cold-induced dormancy (CID) cycles over 4 years. Thirty-one of 33 Prunus species and cultivars were systemically infected following aphid transmission. Systemic infection could not be detected in P. cerasus (sour cherry) and P. x 'Snofozam' (Snow Fountains) despite repeated aphid inoculation attempts. Following grafting of PPV-infected budwood, all 40 species and varieties became infected, although species differed in their susceptibility. Within most species, some individual plants remained PPV negative throughout the study despite repeated inoculations. Infection in some species could be detected only through quantitative reverse transcription (RT)-PCR. Most species displayed clear symptoms, were highly positive by ELISA and RT-PCR, and could be back-inoculated into peach seedlings following CID. Our results indicate that a wide range of native and ornamental Prunus species are susceptible to U.S. isolates of PPV-D.