Potential Prunus host range of PPV-PENN isolates by aphid transmission

Natural spread of Plum pox potyvirus (PPV) occurs by aphid transmission, grafting, or movement of infected nursery stock. Two proven aphid vectors of Plum pox virus, Myzus persicae and/or Brachycaudus persicae were used to transmit North American isolates of PPV to a range of commercial and ornamental Prunus species to test the ability of these species to function as PPV reservoirs. Inoculum sources were 'Lovell' peach seedlings infected with the PPV-PENN-3 or PPV-PENN-4 isolates by previous aphid transmission. Aphids were starved for 30 min, placed onto either detached symptomatic PPV-infected peach leaves or intact peach seedlings, and then allowed a 3-day acquisition-inoculation feeding period from infected tissues to the healthy Prunus seedlings. Seedlings were sprayed with insecticide, placed onto greenhouse benches and observed for 6 to 8 weeks for development of symptoms. Test plants were analyzed by ELISA and PCR, and then back-assayed to 'Lovell' peach seedlings by healthy Myzus persicae. Test plants then were vernalized at 4.1° C for 8-10 weeks. At four-weeks post-vernalization, plants were tested by ELISA and/or RT-PCR to verify systemic infection. Fourteen of the 15 Prunus species tested positive for PPV infection following the initial aphid transmission. Twelve of the 14 infected species were verified to function as potential PPV sources in subsequent aphid transmissions to peach. To date, at least 10 of the 14 Prunus species maintained systemic PPV infection following vernalization. Only P. cerasus (sour cherry) tested negative to PPV infection. Other cherry species, including P. avium, P. cistena, and P. serrulata maintained systemic infection through vernalization. Results suggest that all species tested except P. cerasus, could function as PPV hosts associated with unintentional movement of infected nursery stock and as reservoirs for aphid transmission.