Occurrence of <i>East African cassava mosaic virus</i> ‐Uganda (EACMV‐UG) in Burkina Faso

Abstract

Cassava (Manihot esculenta) is a major staple food crop cultivated throughout Africa, and is affected most severely by cassava mosaic disease (CMD) occurring at high incidence throughout the continent. CMD is caused by cassava mosaic geminiviruses (CMGs) belonging to the genus Begomovirus (family Geminiviridae). The complex of CMGs include seven African species; the three main species are: African cassava mosaic virus (ACMV), East African cassava mosaic virus (EACMV) and South African cassava mosaic virus (SACMV) (Bull et al., 2006). In Uganda, an extremely severe epidemic of CMD has developed since the 1990s and has progressed since then in Uganda's neighbouring countries and Central Africa. The severe CMD phenotype is caused by the synergistic interaction between ACMV and a distinct recombinant strain EACMV-UG, commonly known as the Uganda variant. CMD is reported to be widespread in Burkina Faso (Konatéet al., 1995), but the molecular features of the causal agent have never been investigated. In August/September 2008, leaves were collected from cultivars of local cassava presenting moderate to severe CMD symptoms from the central region around Ouagadougou. Ten leaf samples were tested and found to be positive for the presence of begomoviruses by PCR, using degenerate primers VD360 and CD1266 (Delatte et al., 2005). For two of these samples, complete DNA-A genomes were cloned using the Phi29 DNA polymerase-based rolling circle amplification strategy (Inoue-Nagata et al., 2004) and sequenced by Macrogen Inc. (Korea). One sequence (EMBL-GenBank-DDBJ Accession No. FM877473) showed 97% highest nucleotide identity with ACMV-[Ivory Coast:1999] (AF259894) and ACMV-[Nigeria:Ogoroco:1990] (AJ427910). The second sequence (FM877474) showed 98% nucleotide identity with EACMV-UG [Uganda:Severe2:1997] (AF126806). This is the first report of the Uganda variant in West Africa. These results show that both species ACMV and EACMV-UG affect cassava plantings in Burkina Faso, and suggest a potential risk of the occurrence of a severe epidemic of CMD as in East Africa. This research was funded by the following institutions: CRSBAN/UFR-SVT (University of Ouagadougou), INERA (CNRST, Burkina Faso), Conseil Régional de La Réunion, CIRAD, European Union (FEDER) and GIS Centre de recherche et de veille sanitaire sur les maladies émergentes dans l’Océan Indien (N°PRAO/AIRD/CRVOI/08/03).