First Report of Tomato chlorotic spot virus in Scarlet Eggplant (Solanum aethiopicum) and American Black Nightshade (Solanum americanum) in the United States.
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2015 American Phytopathological Society. All rights reserved. Scarlet eggplant (also known as Ethiopian nightshade or Brazilian eggplant) originated in sub-Saharan Africa and is now grown in many parts of the world as a food, medicinal, or ornamental crop, as well as for use as a rootstock for tomato and common eggplant (Solanum melongena) (Sakhanokho et al. 2014). American black nightshade is a common solanaceous weed in Florida and many subtropical and tropical areas of the world, and has been identified as a natural reservoir host for two tospoviruses [Tomato spotted wilt virus (TSWV) and Groundnut ringspot virus (GRSV)] and an experimental host for a third [Tomato chlorotic spot virus (TCSV)] (Webster et al. 2015). During January and February 2015, two scarlet eggplant and one American black nightshade plants were observed with virus-like symptoms typical of tospoviruses on a vegetable farm in southeast Florida (Palm Beach County). Both TCSV and its western flower thrips (Frankliniella occidentalis) vector were previously detected on tomato and pepper at this farm. A general foliar chlorosis and yellow-orange spotting of mature fruits were observed on the scarlet eggplant samples, and chlorotic foliar ringspots and ring patterns were observed on the American black nightshade (Supplemental file). Samples of all three plants reacted with commercially available TSWV lateral flow immunoassay reagents (Agdia, Inc., Elkhart, IN), indicating the presence of one or more tospoviruses. Total RNA was extracted (RNeasy Plant Mini Kit, Qiagen, Valencia, CA) from symptomatic tissue of these three plant samples and tested for TSWV, GRSV, and TCSV by RT-PCR as previously described (Webster et al. 2015). Primers specific for the TCSV RNA-dependent RNA polymerase (L) gene (TCSV-3Lv/TCSV-3Lvc; 867 bp), nonstructural movement protein (NSm) gene (TCSV-NSmv/TCSV-NSmvc; 835 bp), or nucleocapsid (N) gene (TCSV-Nv2/TCSV-Nvc2; 478 bp) amplified products of the expected size. Primers specific for the N gene of TSWV (Adkins and Rosskopf 2002) or GRSV (Webster et al. 2011) did not amplify products from any sample. TCSV amplicons from one scarlet eggplant sample and the American black nightshade sample were cloned in the pGEM-T vector (Promega, Madison, WI). Five clones of each amplicon were sequenced in both directions and consensus sequences were deposited in GenBank (Accession Nos. KR012984 to KR012989). Sequence analysis demonstrated that all three genes from both plant species shared >98% nucleotide identity with TCSV isolates in GenBank, including previously characterized isolates from tomato, long bean, chili pepper, pepper, jimsonweed, and lettuce in Florida, Dominican Republic, and/or Puerto Rico. TCSV has been previously identified from scarlet eggplant in Paraiba Valley, Sao Paulo, Brazil (Eiras et al. 2002) but, to the best of our knowledge, this is the first report of TCSV naturally infecting scarlet eggplant and American black nightshade in the United States. Expansion of the TCSV host range in the United States provides additional opportunities for spread of this emerging virus to crops of economic importance and potential reservoir species in Florida and elsewhere.
