CBN-V Video Archives - S8-16
The Ugandan Cassava Mosaic Disease Epidemic, an Illustration of the Complexity of African Cassava Mosaic Disease

Pita J.S.^1,2, V.N. Fondong^1,3, A. Sangaré², G.W. Otim-Nape⁴, S. Ogwal⁴ and C.M. Fauquet¹

1.   International Laboratory for Tropical Agricultural Biotechnology (ILTAB), Donald Danforth Plant Science Center, 975 Warson Road, St Louis MO 63132         justpit@danforthcenter.org
2.   Université de Cocody, Laboratoire de génétique, 22 BP 582 Abidjan 22, Côte d’Ivoire              abous@africaonline.co.ci
3.   Institute of Agronomic Research for Development (IRAD), Ekona PMB 25, Buea South, West Province, Cameroon
4.         National Agricultural Research Organization, P.O. BOX 7084, Kampala, Uganda

        An extremely severe cassava mosaic disease (CMD) epidemic has caused increasing concerns in Uganda since 1988. This epidemic, which induced total yield losses and famine in Uganda is now causing serious problems in Kenya, Tanzania, D.R. Congo and Rwanda and it continues to spread throughout the East and Central Africa. From analysis of CMD infected leaf samples collected in Uganda, Cameroon and the Ivory Coast, an increasingly complex picture of CMD was unfolded with evidence for interspecies recombination, synergism and natural pseudo-recombination between the two geminivirus species, African cassava mosaic virus (ACMV) and East African cassava mosaic virus (EACMV). A strain designated as EACMV-UG3, which contains a recombination in its B component, was identified in samples from Uganda. Also demonstrated in these samples was a pseudo-recombinant virus consisting of the EACMV-UG3 B component and the A component of another recombinant, EACMV-UG2, which was directly associated with the Ugandan CMD epidemic. In addition, there was evidence that synergistic interaction between ACMV and EACMV was most probably responsible for the extremely severe CMD symptoms observed on cassava plants growing within the epidemic area in Uganda and in fields visited in Cameroon and the Ivory Coast. The importance of these findings as they relate to the spread of the CMD epidemic in Central Africa are presented.

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