Isolation and Partial Characterization of a Filamentous Virus Associated with Peach Mosaic Disease

A filamentous virus, 752 nm long by 9.25 nm wide and with striations of 3.47 nm in pitch, was isolated from peach mosaic-affected peach. The peach mosaic-associated virus (PMV) has a coat protein subunit molecular mass of 20.5 kDa, and dsRNA bands of 7.0, 6.4, 4.2, and 1.9 × 106 Da, with a number of bands of lower molecular mass ranging in size from 1.3 to 0.3 × 106 Da. The herbaceous host range of PMV includes Chenopodium amaranticolor, C. quinoa, and Nicotiana occidentalis “37B.” The virus was successfully bud-transmitted from infected peach to peach indicator plants, cv. Elberta, which displayed typical peach mosaic symptoms. Attempts to transmit PMV to Prunus avium cv. Bing and P. mahaleb were unsuccessful. In serological assays, PMV polyclonal antibody (PAb) cross-reacted with cherry mottle leaf virus (CMLV). CMLV PAb and CMLV monoclonal antibodies cross-reacted with all isolates of PMV tested. Blocking with skim milk had no effect on the cross-reactions observed. PMV was consistently associated with peach mosaic disease, and the bud transmission studies and serological data suggest that this virus is the causal agent of peach mosaic disease. Data indicating that there is no relationship between peach latent mosaic viroid and peach mosaic disease was also obtained. PMV and CMLV appear to be closely related viruses, with identical coat protein subunit size and dsRNA profiles.