Incidence and characterization of cassava mosaic viruses in improved and local cultivars in Sierra Leone

In Sub-Sahara Africa, Cassava Mosaic Disease (CMD) is the major important viral disease of cassava which threatens production, livelihoods and food security. Frequently CMD is due to the Africa Cassava Mosaic Virus (ACMV), East African Cassava Mosaic Virus (EACMV) and the Ugandan strain of the East African virus (EACMV-UG). The present study investigated the prevalence of these three viruses in 27 cultivars (three improved and 24 local) of cassava grown across all key agro-ecological zones and regions in Sierra Leone. Leaf samples from each of these varieties with symptoms as well as asymptomatic ones were harvested from a clonal garden established on the Njala University Campus. Deoxyribonucleic acid (DNA) extracted from these samples was assessed with Marker Assisted Selection (MAS) for ACMV, EACMV and EACMV-UG using polymerase chain reaction (PCR) and primers designed to amplify replica regions of the DNA-A components of these viruses. The results revealed the ACMV is very common (26 out of 27 samples), while EACMV and EACMV-UG are less common (3 out of 27). Samples with EACMV-UG also had ACMV. These findings are of importance to future breeding programs for resistance to CMD with the aim of producing multiple viral resistant clones for increased food security in the country.   Key words: Cassava, DNA, characterization, mosaic viruses, incidence, varieties, Sierra Leone.