Incidencia en el campo e identificación del Southern Bean Mosaic Virus (Cowpea strain)

Abstract

During a survey for virus incidence in commercial cowpea fields in Western Nigeria in 1973, a seed-transmissible virus identified serologically as southern bean mosaic (SBMV-CS) was found at three different locations. In all instances the virus occurred as a mixed infection with cowpea yellow mosaic virus (CYMV). They were separated by employing the differences in their host ranges and physical properties. Inoculation of one of the isolates of SBMV-CS to different hosts indicated that the host range of the virus was restricted to the Leguminosae. Reactions of twenty-five cowpea cultivars to manual inoculation with the virus varied from immune to severe infection leading to death of plants. Te virus was transmitted through the seeds of at least one white-seeded local cowpea variety. Properties of the virus in crude sap were: thermal inactivation (10 min exposure) at 90 C (occasionally at 95 C) but not at 85 C; dilution end-point, 10-0 —10-7; and ageing in vitro, 15 days. Purified virus preparations contained spherical particles 28.0 ± 1.0 nm diameter which sedimented as a single component in sucrose density gradient or analytical ultracentrifugation at S20,w = 114. Antiserum prepared against the virus reacted with the bean strain, the cowpea strain, and the Ghana cowpea strain of SBMV. Spur formation indicated that the isolate was related but distinct from previously studied isolates of SBMV.