DETECTION OF A POTYVIRUS RELATED TO GUINEAGRASS MOSAIC-VIRUS INFECTING BRACHIARIA SPP IN SOUTH-AMERICA

A filamentous virus approximately 775 nm long was isolated from varieg ated plants of the tropical forage grass Brachiaria spp. collected in Colombia and Brazil, South America. Ultrathin sections of symptomatic leaf tissue showed cylindrical inclusions (scrolls) in the cytoplasm o f infected cells. The virus was transmitted mechanically to selected s pecies of Brachiaria, Panicum, and Paspalum but not to maize, sorghum, or sugarcane. The virus was also transmitted from and to B. brizantha by the aphid Myzus persicae in a nonpersistent manner. The virus was not seedborne in Brachiaria spp. Purified virus preparations had an A2 60/280 ratio of 1.30 and exhibited capsid protein heterogeneity (M(r) 41, 34, 32, and 30 kDa) as determined by SDS-PAGE. The virus was close ly related serologically to guineagrass mosaic virus from Africa, dist antly related to watermelon mosaic virus-2, and not related to maize d warf mosaic, sorghum mosaic, and sugarcane mosaic viruses. Results of our serological and pathogenicity tests suggest that the virus isolate d from Brachiaria spp. is a strain of guineagrass mosaic potyvirus (GG MV). This would be the first report on the occurrence of GGMV in the A mericas.