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New Disease Reports (2001) 4, 4.
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The occurrence of the Uganda Variant of East African Cassava Mosaic Virus (EACMV-Ug) in western Democratic Republic of Congo and the Congo Republic defines the westernmost extent of the CMD pandemic in East/Central Africa

P. Neuenschwander 1*, J.d'A. Hughes 2, F. Ogbe 2, J.M. Ngatse 3 and J.P. Legg 4,5

*p.neuenschwander@cgiar.org

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Accepted: 09 Aug 2001

Following reports of the occurrence of severe cassava mosaic virus disease (CMD) in the Democratic Republic of Congo (DRC) and Congo Republic, we investigated the possibility that the severe disease was caused by the Uganda variant of East African cassava mosaic virus (EACMV-Ug) (family Geminiviridae; genus Begomovirus), which causes unusually severe CMD symptoms. Cassava leaves with severe CMD symptoms were collected in August 1999 from 9 fields in Lekana, N'Sah and Abala-Ndolo in the central part of Congo Republic (Fig. 1), and leaves with a range of symptoms were collected in December 2000 from 30 CMD-affected plants from 12 fields in Kinshasa and Bas-Congo Provinces of DRC. Samples from the Congo Republic were preserved in alcohol and tested for the presence of cassava mosaic geminiviruses (CMGs) at IITA-Ibadan by PCR using non-specific EACMV primers and specific primers for African cassava mosaic virus (ACMV), EACMV and EACMV-Ug (Harrison et al., 1997; Zhou et al., 1997). For samples from the DRC, whole plant DNA was extracted locally, but viruses were identified by PCR using specific primers for ACMV and EACMV-Ug in Uganda.

Seven of the nine samples from the Congo Republic contained both ACMV and EACMV-Ug, one contained EACMV-Ug alone and one produced a product with general but not specific EACMV primers, results suggesting it was a strain of EACMV. Nine of the DRC samples contained both ACMV and EACMV-Ug and six of these were from plants with very severe CMD symptoms (Fig. 2). Sites in the DRC from which EACMV-Ug-infected samples were collected were distributed throughout the area surveyed (Fig. 1).

Our results confirm the occurrence of EACMV-Ug in West/Central Africa and suggest that the area affected by this virus variant, initially described in association with the East African CMD pandemic, extends much further westwards than previously recognised (Legg, 1999).

Figure1+
Figure 1: Sampled zones of the Congo Republic and the Democratic Republic of Congo in which the Uganda Variant of EACMV (EACMV-Ug) was identified (yellow) from CMD-diseased cassava leaf samples, 1999-2000.
Figure 1: Sampled zones of the Congo Republic and the Democratic Republic of Congo in which the Uganda Variant of EACMV (EACMV-Ug) was identified (yellow) from CMD-diseased cassava leaf samples, 1999-2000.
Figure2+
Figure 2: Severe CMD associated with mixed ACMV/EACMV-Ug infection.
Figure 2: Severe CMD associated with mixed ACMV/EACMV-Ug infection.

References

  1. Harrison, BD, Zhou X, Otim-Nape GW, Liu Y, Robinson DJ, 1997. Role of a novel type of double infection in the geminivirus-induced epidemic of severe cassava mosaic in Uganda. Annals of Applied Biology 131, 437-448.
  2. Legg JP, 1999. Emergence, spread and strategies for controlling the pandemic of cassava mosaic virus disease in east and central Africa. Crop Protection 18, 627-237.
  3. Zhou X, Liu Y, Calvert L, Munoz C, Otim-Nape GW, Robinson DJ and Harrison BD, 1997. Evidence that DNA-A of a geminivirus associated with severe cassava mosaic disease in Uganda has arisen by interspecific recombination. Journal of General Virology 78, 2101-2111.
This report was formally published in Plant Pathology

©2001 The Authors