Molecular, ultrastructural and biological characterization of Pennsylvania isolates of plum pox potyvirus (PPV)

Authors: Schneider, William; Damsteegt, Vernon; GILDOW, FREDERICK - Pennsylvania State University; Stone, Andrew; Sherman, Diana; LEVY, LAURENE - Animal And Plant Health Inspection Service (APHIS); MAVRODIEVA, VESSELA - Animal And Plant Health Inspection Service (APHIS); RICHWINE, NANCY - Pennsylvania Department Of Agriculture; WELLIVER, RUTH - Pennsylvania Department Of Agriculture; Luster, Douglas - Doug

Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/13/2011
Publication Date: 5/1/2011
Citation: Schneider, W.L., Damsteegt, V.D., Gildow, F.E., Stone, A.L., Sherman, D.J., Levy, L.E., Mavrodieva, V., Richwine, N., Welliver, R., Luster, D.G. 2011. Molecular, ultrastructural and biological characterization of Pennsylvania isolates of plum pox potyvirus (PPV). Phytopathology. 94:528-533.

Interpretive Summary: Plum pox virus (PPV) was first identified in Pennsylvania in 1999, causing significant worry among peach growers nationwide. The isolate was identified as a member of the D strain of PPV, and all of the future control efforts were based on assumptions that the Pennsylvania isolates would behave and spread similarly to the D strain isolates found all across Europe. In an effort to better guide regulators, the experiments in this paper sought to better characterize the Pennsylvania isolates of PPV in terms of the genetic sequence, the form of the virus, and the biology in terms of aphid transmission and symptom severity. This work demonstrates that the PPV D isolates are most closely related to other western hemisphere isolates from Chile and Canada. This suggests a single introduction of PPV into the western hemisphere, but cannot conclusively demonstrate the source for Pennsylvania PPV. In addition, Pennsylvania PPV is very similar to European D strains in terms of virus structure and alternative hosts, but differs from European D strains in terms of aphid transmission and symptom development. The Pennsylvania strains are more readily transmitted by aphids, and cause slightly stronger symptoms than European D strains. However, the Pennsylvania strains are not nearly as transmissible or as pathogenic as the European M strains which are the most pathogenic forms of plum pox. This information is useful for the understanding the effects of PPV on peach.

Technical Abstract: Plum pox potyvirus (PPV) was identified in Pennsylvania in 1999. The outbreak was limited to a four county region in southern Pennsylvania. Initial serological and molecular characterization indicated that the isolates in Pennsylvania belong to the D strain of PPV, as do all the other PPV isolates in the Western hemisphere. The Pennsylvania isolates were characterized by sequence analysis, electron microscopy and biological characterization to determine how these isolates related to their previously studied European counterparts. At the sequence level Pennsylvania (PPV-Penn) isolates were more closely related to each other than to any other PPV-D strains, and isolates from the US, Canada and Chile were more closely related to each other than to described European isolates. Based on sequence analyses the PPV-Penn isolates exist as two clades, suggesting the possibility of multiple introductions. Electron microscopy analysis of PPV-Penn isolates indicated that the virions were similar morphologically with other potyviruses, and the PPV-Penn isolates induced cytopathologies characteristic of potyviruses. PPV-Penn isolates had a similar herbaceous host range as European D isolates. There were distinct differences in the transmission efficiencies of the two PPV-Penn clades using Myzus persicae and Aphis spiraecola as vectors. In addition, both PPV-Penn clades were transmitted by M. persicae more efficiently than a European D isolate, but less efficiently than a European M isolate.