Isolation and Characterization of a Carmo-like Virus from Calibrachoa Plants

Abstract

Spherical virus particles approximately 29 to 31 nm in diameter were isolated from Calibrachoa plants showing leaf mottling and chlorotic blotch symptoms. The virus was mechanically transmitted to Chenopodium amaranticolor, C. capitatum, C. quinoa, Nicotiana benthamiana, and N. clevelandii plants, but was not transmitted by green peach aphid (Myzus persicae), sweet potato whitefly (Bemisia tabaci), silverleaf whitefly (B. argentifolii), greenhouse whitefly (Trialeurodes vaporarium), or banded-wing whitefly (T. abutilonea). Virions contained a single species of single-stranded RNA of approximately 4.0 kb and a single capsid protein of approximately 41 kDa. The double-stranded (ds)RNA pattern consistently revealed one major band of about 4.0 kbp, and three minor dsRNA of approximately 3.1, 1.6, and 1.3 kbp. The virus-infected plants reacted with a homologous polyclonal antiserum in indirect enzyme-linked immunosorbent assay. The genome contained a sequence of a highly conserved motif of the RNA-dependent RNA-polymerase associated with the genus Carmovirus, and shared 94% identity with Carnation mottle virus (CarMV). However, the Calibrachoa virus and CarMV were distinct serologically and in host range. Based on the host ranges, particle morphology, dsRNA profile, properties of particles in sap, and features of the genome and protein, we concluded that the recently observed Calibrachoa disease is caused by a previously undescribed carmovirus on Calibrachoa plants. We propose to name this virus Calibrachoa mottle virus (CbMV).