Submitted to: Journal of General Virology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/28/2007
Publication Date: 9/10/2007
Citation: Wallis, C.M., Schneider, W.L., Stone, A.L., Sherman, D.J., Damsteegt, V.D., Gildow, F.E. 2007. Identification of a mutation in the plum pox potyvirus nib gene associated with adaptation to pea (pisum sativum). Journal of General Virology. 88:2839-2845.
Interpretive Summary: PPV was first identified in the US in 1999. Since then the USDA has attempted to eradicate the disease. A key factor in the eradication effort is understanding the possibility that PPV may develop reservoirs in alternative hosts. If such reservoirs develop easily, the eradication effort is unlikely to succeed. In order to investigate this, PPV isolates from Pennsylvania were transmitted from their original host peach to peas, simulating what could happen in the field. The initial passages to pea were mostly unsuccessful, but once a PPV population was established in peas it adapted to the host over time and continued transmission to new peas. A specific mutation was identified that was associated with PPV adaptation to peas. This work suggests that while it is possible for PPV to infect alternative hosts (potential reservoirs), there is a “trade off” in fitness. The mutation that allows PPV to successfully infect peas reduces the virus’s ability to infect peaches, making herbaceous hosts an unlikely alternative reservoir.
Technical Abstract: Plum pox potyvirus (PPV) populations from peaches adapt to herbaceous hosts, characterized by a reduction in time to symptom development, increases in inoculation efficiency and increased titers. PPV adaptation was studied using pea (Pisum sativum) as an alternative host. Two isolates of PPV from peaches were inoculated and passaged in peas ten times using either aphid or mechanical inoculation, generating four independent passage lines. Transmission efficiency from peach to pea improved using mechanical inoculation or aphid vectors. Sequence analyses of both PPV populations sequentially inoculated to pea identified a specific mutation occurring consistently in the NIb gene, when compared to the same PPV isolates passaged in parallel in peach. The mutation allowed PPV to replicate up to twenty times faster in the new host. Pea-adapted strains of PPV at every passage were also tested for their ability to infect the original host, peach. Regardless of the number of previous passages, all pea-adapted PPV strains consistently infected peach using aphid inoculation.