A SOBEMOVIRUS HINDERING THE UTILIZATION OF CALOPOGONIUM MUCUNOIDES ASA FORAGE LEGUME IN THE LOWLAND TROPICS

The cultivation of calopo, Calopogonium mucunoides, as a promising for age legume for the lowland tropics, was hindered by its susceptibility to a severe yellow mosaic disease observed in the Eastern Plains of C olombia. An isometric virus ca. 28 nm in diameter was observed by elec tron microscopy in leaf extracts and purified preparations, and in phl oem cells of systemically infected calopo plants. The virus was transm itted by mechanical means and by the chrysomelid beetle Diabrotica bal teata. The host range of the virus was restricted to the legumes Phase olus vulgaris, Vigna unguiculata, V. radiata, Centrosema spp., and Sen na occidentalis. The physical and chemical properties of the calopo vi rus were similar to those reported for the sobemovirus group, and the virus was antigenically related to the bean and cowpea strains of sout hern bean mosaic virus (SBMV). However, the host range of the calopo v irus differed from the pathogenicity spectra of the bean, cowpea, Ghan aian, and Mexican strains of SBMV. Nucleotide sequence analysis of a 6 09 bp fragment amplified from the coat protein region of the calopo so bemovirus revealed similarities of 81.8 and 66.1% with the correspondi ng regions of the bean and cowpea strains, respectively, of SBMV. The respective homologies increased to 83.7 and 67.8% when the deduced ami no acid sequences of these viruses were compared. It is concluded that the mosaic disease of calopo is caused by a previously undescribed so bemovirus for which the name calopo yellow mosaic virus is suggested.