A virus causing chlorosis of veins, mosaic, green banding along veins and downward leaf rolling in sesame in Georgia, USA, was isolated from sesame plants grown from seed imported from the Sudan. The virus was sap-transmissible to species of Amaranthaceae, Chenopodiaceae, Cucurbitaceae, Leguminosae and Solanaceae. Chenopodium amaranticolor was used as a local lesion assay host and the pea cultivar Little Marvel as the propagation host for purification. The virus was non-persistently transmitted by Aphis craccivora and Myzus persicae but was not transmitted through sesame seed. The virus remained infective in buffered leaf sap of Nicotiana benthamiana at a dilution of 10-5 after storage for 9 d at 25 degrees C and heating for 10 min to 55 degrees (but not to 60 degrees ). The virus induced cylindrical cytoplasmic inclusions in infected tissues of Lupinus albus. Purified virus preparations yielded flexuous filamentous particles that contained a major polypeptide of c. 33 kDa and 1 nucleic acid species with a MW of 3.1 x 106. In indirect ELISA, the virus reacted positively to antisera of blackeye cowpea mosaic, peanut green mosaic, peanut stripe, pea seed-borne mosaic, soybean mosaic, tobacco etch, watermelon mosaic 2 and zucchini yellow mosaic potyviruses but not to watermelon mosaic virus I and peanut mottle and bean common mosaic potyviruses. In reciprocal tests, peanut stripe potyvirus and watermelon mosaic 2 potyvirus, but not peanut green mosaic, peanut mottle, pea seed-borne mosaic, blackeye cowpea mosaic, soybean mosaic, and tobacco etch potyviruses, reacted with the antiserum for the sesame virus. On the basis of these properties, the causal virus is identified as an unnamed potyvirus isolate causing sesame mosaic.