First Report of East African Cassava Mosaic Begomovirus in Ghana

Virus species causing cassava mosaic disease have been categorized into three classes based on their reaction with monoclonal antibodies (MAbs) and their distribution (2). These viruses have different, scarcely overlapping distribution: African cassava mosaic begomovirus (ACMV) occurs in Africa west of the Rift Valley and in South Africa; East African cassava mosaic (EACMV) occurs in Africa east of the Rift Valley and in Madagascar; and Indian cassava mosaic virus (ICMV) occurs in India and Sri Lanka (2). During 1998, surveys were conducted in farmers' fields in Ghana to assess the incidence and reaction of local cassava cultivars to cassava mosaic disease. Leaf samples from symptomatic plants were indexed by triple antibody sandwich-enzyme-linked immunosorbent assay with crude extracts and monoclonal antibodies obtained from the International Institute of Tropical Agriculture (IITA). Each sample was assayed with monoclonal antibody SCR 23, which detects ACMV and EACMV, SCR 33, which detects ACMV, and SCR 58, which detects ICMV. None of the samples reacted with SCR 58. Two of the samples collected from the western region of Ghana produced strong reactions with MAb SCR23 but did not react with ACMV-specific MAb SCR 33. This result was consistent in three separate experiments conducted on the samples, confirming that the virus was EACMV and not ACMV. The results extend the work by Ogbe et al. (1) and provide further evidence of the occurrence of EACMV in west Africa. References: (1) F. O. Ogbe et al. Plant Dis 83:398, 1999. (2) M. M. Swanson and B. D. Harrison. Trop. Sci. 34:15, 1994.