Presence of Tobacco Ringspot Virus in Aeonium spp.

In March 2011 plants of Aeonium spp., family Crassulaceae, showing chlorotic spots and rings on both leaf surfaces were observed in a private garden in the vicinity of Salerno (southern Italy). Electron microscope observations of leaf dips from several of these plants revealed the presence of isometric virus-like particles ca. 30 nm in diameter, some of which were partially or completely penetrated by the negative stain, as if they were devoid of nucleic acid in part or totally. A number of herbaceous hosts were successfully infected after mechanical inoculation with sap expressed from symptomatic Aeonium plants. For example, Nicotiana benthamiana and Lycopersicon esculentum (tomato) were systemically invaded and reacted with mottling and deformation of the leaves and yellowish concentric rings and line patterns, respectively. A virus with isometric particles indistinguishable from those seen in leaf dips was readily purified from symptomatic N. benthamiana leaves. RNA extracted from virus particles and analyzed in ethidium bromide-permeated agarose gels migrated as two separate bands. These were recovered and used as template for synthesizing cDNAs, which were cloned and partially sequenced. The viral genome was confirmed to consist of two distinct RNA species which were molecularly similar, but not identical, to RNA-1 and RNA-2 of Tobacco ringspot virus (TRSV) (Sanfaçon et al., 2012). TRSV has been intercepted in Italy in imported gladiolus bulbs (Bellardi and Marani, 1985) but, to our knowledge, has never been found in a cultivated plant. Its potential danger to economical crops like tomato is to be taken into account, especially should the presence of a nematode vector be ascertained.