Archivio Journal of Plant Pathology

Abstract:

In March 2011 plants of Aeonium spp., family Crassulaceae, showing chlorotic spots and rings on both leaf surfaces were ob- served 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 parti- cles ca. 30 nm in diameter, some of which were partially or com- pletely 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, Nico- tiana benthamiana and Lycopersicon esculentum (tomato) were systemically invaded and reacted with mottling and deformation of the leaves and yellowish concentric rings and line patterns, re- spectively. 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 ana- lyzed 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 se- quenced. The viral genome was confirmed to consist of two dis- tinct RNA species which were molecularly similar, but not identi- cal, to RNA-1 and RNA-2 of Tobacco ringspot virus (TRSV) (San- façon et al., 2012). TRSV has been intercepted in Italy in import- ed gladiolus bulbs (Bellardi and Marani, 1985) but, to our knowl- edge, has never been found in a cultivated plant. Its potential danger to economical crops like tomato is to be taken into ac- count, especially should the presence of a nematode vector be as- certained.