First Report of Tomato chlorotic spot virus Infecting Spilanthes oleracea in Brazil.

Abstract

Spilanthes oleracea L., popularly known as toothache plant, belongs to the family Asteraceae and is a South American native plant. Fresh leaves can be eaten for their medicinal properties or used by the cosmetics industry for their spilol contents. Plants showing leaf deformation that were collected in a field in São Paulo State, Brazil in March 2005 were suspected to be infected by a virus. Electron microscopy of leaf dip preparations of symptomatic plants revealed pleiomorphic particles typical of tospoviruses. Extracts from these plants prepared with 0.01 M sodium phosphate buffer, pH 7.0, containing 1% sodium sulfite were mechanically inoculated to indicator plants. Chenopodium amaranticolor and Gomphrena globosa were symptomless. Necrotic local lesions were observed on C. quinoa. Necrotic local lesions followed by a systemic necrosis that caused the death of the plants were observed on Datura stramonium, Nicotiana glutinosa, and N. tabacum 'TNN' and 'Turkish'. Concentric rings followed by systemic necrosis and plant death were induced on N. rustica, N. tabacum 'Havana 425', N. clevelandii, Physalis floridana, Capsicum annum 'Magda', and Solanum lycopersicum 'Santa Clara'. Total RNA was extracted (1) from infected S. oleracea and N. rustica plants for reverse transcription-PCR amplification with tospovirus specific primers BR60 (5' CCCGGATCCTGCAGAGCAATTGTGTCA 3') and BR65 (5' ATCAAGCCTTCTGAAAGTCAT 3') (2), which amplified an approximate 440-bp fragment covering part of the nucleocapsid protein gene. This fragment was sequenced (EMBL Accession No. AM887766) and showed 99% nt sequence identity with Tomato chlorotic spot virus (TCSV) (GenBank Accession No. AF521102), a tospovirus species (3). To our knowledge, this is the first report of a tospovirus infecting S. oleracea in Brazil and indicates that this plant might constitute a reservoir of TCSV or other tospoviruses that could also infect tomato and pepper plants.