First Report of a Tobamovirus in Dieffenbachia and Impatiens.

Tobamoviruses were detected in two ornamental plants, Dieffenbachia picta (Araceae) and Impatiens hawkeri (Balsaminaceae), from different counties in São Paulo State, Brazil. Symptoms were chlorotic spots and rings in D. picta and mosaic, blistering, and leaf deformation in I. hawkeri. Mechanical transmission from both species induced different kinds and intensities of symptoms in the same experimental hosts (Balsaminaceae, Chenopodiaceae, and Solanaceae), except Gomphrena globosa, which was infected only by the isolate from D. picta. The viruses did not infect Cucurbitaceae and Fabaceae. Indirect enzyme-linked immunosorbent assay performed with extracts from infected Nicotiana tabacum 'White Burley' and antisera against Cucumber green mottle, mosaic, Frangipani mosaic, Odontoglossum ringspot, Ribgrass mosaic, Tobacco mosaic (TMV), Tomato mosaic, Turnip vein clearing, and Youcai mosaic viruses (genus To-bamovirus) was positive only for TMV. Furthermore, the viruses isolated from D. picta and I. hawkeri cross-reacted with their heterologous antisera. Two sense primers for regions ≍200 and 90 nt upstream of the start codon and an antisense primer ≍60 nt downstream of the terminal codon of the coat protein (CP) gene were designed for two amplification assays. Migrating fragments the same size as the reverse-transcription polymerase chain reaction products from the TMV type strain (479 and 800 bp with internal and external primers, respectively) were produced. The CP gene sequence will allow comparison and identification of the two viruses isolated from D. picta and I. hawkeri.