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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

2002; Wiley; Volume: 51; Issue: 3 Linguagem: Inglês

10.1046/j.1365-3059.2002.00698.x

1365-3059

Peter Neuenschwander, J. d’A. Hughes, F. Ogbe, J. M. Ngatse, J. P. Legg,

Plant-Microbe Interactions and Immunity

Following reports of the occurrence of severe cassava mosaic virus disease (CMD) in the Democratic Republic of Congo (DRC) and Congo Republic, 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, was investigated. Cassava leaves with severe CMD symptoms were collected in August 1999 from nine fields in Lekana, N'Sah and Abala-Ndolo in the central part of Congo Republic, 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 at IITA-Ibadan by PCR using nonspecific 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, suggesting that 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. Sites in the DRC from which EACMV-Ug-infected samples were collected were distributed throughout the area surveyed. These 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 recognized (Legg, 1999).