Incidence and distribution of cassava mosaic begomoviruses in Côte d’Ivoire

Abstract Cassava mosaic disease (CMD) caused by the whitefly-transmitted begomoviruses (family Geminiviridae) is a major threat to production of cassava (Manihot esculenta Crantz) in Côte d'Ivoire. A survey was conducted in the major production zones in Côte d'Ivoire to assess the incidence, severity, and distribution of cassava viral diseases. At each survey site, up to ten plants were assessed for symptom severity; incidence and samples were taken for virus testing. Techniques based on polymerase chain reaction (PCR) were used for the detection of cassava mosaic begomoviruses (CMBs) in the sampled leaves. Incidence of CMD varied from 0 to 100% and symptom severity from 1 to 5. Incidence differed significantly between the various agro-ecological zones (P<0.001), but severity was the same in those zones. Out of the 335 samples tested, African cassava mosaic virus (ACMV) was detected in 43.3%, East African cassava mosaic Cameroon virus (EACMCV) in 5.7%, and both ACMV and EACMCV in 31.3%; 19.7% of the samples analyzed were negative to all the viruses tested. None of the samples was tested positive to the East African cassava mosaic virus-Uganda (EACMV-Ug). These results suggest high incidence of CMD in the cassava production zones in Côte d'lvoire and underscores a need for implementation of control measures including phytosanitary measures with utilization of CMD-free materials for planting and adoption of resistant varieties.