New Disease Reports (2008) 18, 20.

First report of the occurrence of East African cassava mosaic virus-Uganda (EACMV-UG) in Angola  

P. Lava Kumar1*, S.A. Akinbade1, A.G.O. Dixon1, N.M. Mahungu2, M.P. Mutunda3, D. Kiala3, L. Londa3 and J.P. Legg4,5

1 International Institute of Tropical Agriculture (IITA), PMB 5320, Ibadan, Nigeria
2 IITA, Chitedze Research Station, P.O. Box 30258, Lilongwe 3, Malawi
3 Instituto de Investigação Agronomica, P.O. Box 2104, Avenida Deolinda Rodrigues KM-5, Luanda, Angola
4 IITA, P.O. Box 6226, Dar-es-Saalam, Tanzania
5 Natural Resources Institute, Chatham Maritime, ME4 4TB, UK

*L.kumar@cgiar.org

Accepted: 19 Sep 2008

Cassava mosaic disease (CMD) is the major production constraint on cassava (Manihot esculenta) in Angola. Previous reports derived from single samples recorded the presence of African cassava mosaic virus (ACMV) and East African cassava mosaic virus (EACMV) in Angola. Regional CMD monitoring initiatives have predicted the spread into northern Angola of EACMV-Uganda (-UG), the unusually virulent recombinant strain associated with the African CMD pandemic (Legg et al., 2006). In view of this threat, an assessment survey was conducted in north and central Angola in April 2008.

Eighteen cassava fields were sampled in Bengo, Cuanza Norte, Malanje and Uige Provinces. Moderate to severe CMD symptoms were observed in most fields. Sixty-three of 65 samples obtained from these fields tested positive in TAS-ELISA using monoclonal antibody SCR 20. PCR was performed using primer pairs previously described for the specific identification of ACMV, EACMV, EACMV-UG, East African cassava mosaic Cameroon virus (EACMCV) and Indian cassava mosaic virus (ICMV) (Ogbe et al., 2003), East African cassava mosaic Malawi virus (EACMMV) (Zhou et al., 1998), East African cassava mosaic Zanzibar virus (EACMZV) (Were et al., 2004) and South African cassava mosaic virus (SACMV) in mixed infections. This revealed the occurrence of ACMV, EACMV and EACMV-UG, but not EACMZV, EACMMV, SACMV or ICMV. Single infections of ACMV and EACMV were detected in 32.3% and 9% of samples, respectively. Mixed infections of ACMV with EACMV, EACMV with EACMV-UG and all three viruses were detected in 35.3%, 1.5% and 16.9% of samples, respectively. ACMV, detected in 84.6% of samples, was the predominant species, followed by EACMV (63%) and EACMV-UG (18.5%). Significantly, EACMV-UG occurred most frequently in the northernmost part of the surveyed area (Uige Province) immediately to the south of the Bas Congo region of the Democratic Republic of Congo, already known to be affected by the pandemic. These findings significantly broaden the known geographical extent of the CMD pandemic and draw attention to the urgent need for the large-scale deployment of resistant cassava varieties, which have been used to reduce losses in pandemic-affected regions of East Africa.

Figure1
Figure 1: Severe symptoms of EACMV-UG in cassava in a farmer’s field in Uige province, Angola
Figure2
Figure 2: CMD incidence in various cassava fields surveyed in Angola. Areas of EACMV-UG occurrence are indicated with yellow circles.

Acknowledgements

This research was supported by the IITA Strategic Funding Program.


References

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Ogbe FO, Thottappilly G, Dixon AGO, Atiri GI and Mignouna HD. 2003. Variants of East African cassava mosaic virus and its distribution in double infections with African cassava mosaic virus in Nigeria. Plant Disease 87, 229-232.

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Zhou X, Robinson DJ and Harrison BD, 1998. Types of variation in DNA-A among isolates of East African cassava mosaic virus from Kenya, Malawi and Tanzania. Journal of General Virology 79, 2835–2840.

©2008 The Authors