Technical Abstract: Calibrachoa mottle virus (CbMV), a putative Carmovirus was first isolated and reported by Liu et al. from infected Calibrachoa plants. During the spring of 2003, petunia samples sent to testing services at Agdia Inc. (Elkhart, IN) tested positive for CbMV by enzyme-linked immunosorbent assay (ELISA) and lateral flow immunoassay (ImmunoStrips®). These samples also tested positive by both Carmovirus group specific PCR primers and by immunocapture PCR. RNA extracted from these samples with RNeasy Plant Kit (Qiagen Inc., Valencia, CA) hybridized with digoxigenin labeled probe derived from purified CbMV viral RNA. Among the samples that tested positive for CbMV one symptomatic sample also tested positive for Tobacco mosaic virus (TMV). From samples that tested positive for CbMV only, mechanical inoculations were made to Chenopodium quinoa at the USDA-ARS greenhouse in Salinas, CA. The representative single local lesions were used to sub-inoculation additional C. quinoa plants. The resulting local lesions from this sub-inoculation wee freeze dried and further used as virus inoculum (CbMV petunia). Similar inoculum was made with CbMV isolated from Calibrachoa plants (CbMV Calibrachoa). Virus-free Petunia hybrida cultivars Surfinia® 'Baby Pink' and Surfinia® 'Violet' (Jackson & Perkins Inc., Somis, CA) were mechanically inoculated with both CbMV petunia and CbMV Calibrachoa. Four weeks post-inoculation of all plants were tested by ELISA for the presence of CbMV. In greenhouse conditions 14.3% of the 'Baby Pink' plants were positive to CbMV petunia whereas none was positive for CbMV Calibrachoa. 'Violet' plants were 64.3% and 33.3% positive for CbMV petunia and CbMV Calibrachoa, respectively. None of the positive plants expressed virus-like symptoms. Virus particles resembling those of CbMV were observed from infected petunia plants by transmission electron microscopy in leaf-dip preparations. This is the first report of CbMV infecting petunia. Commercial reproduction of petunia plants and maintenance of genetic mother stock are usually by vegetative propagations. CbMV can be transmitted mechanically and is readily propagated along with its host. In order to produce healthy petunia plants, virus-like mother stock should be used, which requires regular screening of mother stock for CbMV.