Cynoglossum officinale, a New Natural Host of Alfalfa mosaic virus

Cynoglossum officinale L. (family Boraginaceae), hound's-tongue, is a medicinal plant whose roots are used for their astringent and healing properties and for their sedative, calming, and slightly narcotic effects. This species, originating from Europe where it grows wild in mountainous fields, is cultivated only for its medicinal properties. Epidemiological surveys performed in the Emilia Romagna Region of northern Italy in the spring and autumn of 2001 revealed the presence of virus-like symptoms on C. officinale cultivated in two different locations. In the Botanical Garden of the University of Bologna, the plants showed stunting, interveinal chlorotic spots, midrib necrosis, and scarce or no seed production. In the experimental field of the Agriculture Faculty of Bologna (Imola), the plants exhibited stunting, interveinal chlorotic spots, and reduction of leaf lamina. Mechanical inoculations of sap from symptomatic leaves caused typical symptoms of Alfalfa mosaic virus (AlMV) on Chenopodium amaranticolor Coste & Reyn. (local chlorotic, necrotic lesions and systemic chlorotic vein streaking), Vigna unguicolata (L.) Walp., and Phaseolus vulgaris L. (local necrotic lesions). Using an electron microscope, examination of leaf sap obtained from infected plants stained with uranyl acetate and phosphotungstic acid did not show the presence of elongated virus particles. Serological tests, such as immunoelectron microscopy, gold-labeled decoration, and protein A sandwich indirect enzyme-linked immunosorbent assay using antiserum to AMV (PVAS 92, American Type Culture Collection, Manassas, VA, and AlMV-Vinca minor L., from the DiSTA collection, Bologna, Italy as a control), gave positive reactions, indicating that the virus in question was AlMV. To our knowledge, this is the first report of virus infection on C. officinale, a new natural host of AlMV.