CBN-V Video Archives - S8-05
Tackling the Cassava Mosaic Disease (CMD) Challenge in Sub-Saharan Africa: The Role of Host-plant Resistance and Germplasm Deployment

Dixon A.G.O.¹, J.B.A. Whyte², N.M. Mahungu³ and S.Y.C. Ng¹

1. International Institute of Tropical Agriculture (IITA), P. M. B. 5320, Ibadan, Nigeria A.DIXON@CGIAR.ORG
2. East Africa Root Crops Research Network and IITA-Eastern and Southern Africa Regional Center, Kampala, Uganda
3. Southern Africa Root Crops Research Network, Lilongwe, Malawi

        Cassava mosaic disease (CMD) is the most widespread and economically damaging disease of cassava in Africa. With annual production losses of about $1.2–2.3 billion. Earlier breeding for resistance to CMD at IITA took advantage of resistant clone 58308 obtained from the interspecific hybridization program in East Africa as the sole source of resistance. This led to the development of several elite genotypes such as TMS 30572 and TMS 4(2)1425, that combine high and stable yields with good consumer quality and acceptable levels of resistance to CMD. The delivery of these elite genotypes to national programs for testing under local environmental conditions led to the widespread and successful deployment of CMD resistant clones in several countries. As IITA was deploying these resistant materials, the concern to diversify resistance and expand the gene pool was clearly recognized and vigorously pursued. New and diverse sources of resistance better than that of the genetic stock 58308 were identified from a collection of landraces from West Africa. The establishment of the genetic relationships and heterotic patterns, mechanisms and genetic control of resistance of these resistant landraces enabled efficient incorporation into IITA’s breeding populations and Latin American germplasm with known adaptation to specific relevant agroecologies and potentially new production areas in Africa. Over 400 improved genotypes are now available in the multi-trait package of high and stable yields, diverse and high levels of multiple disease and pest resistance, especially to CMD. The improved genotypes have desirable plant architecture and root quality characteristics for different end uses. They have been distributed to national systems and are at various levels of utilization. They are also of global value as source materials to combat CMD caused by Indian cassava mosaic virus in India and potentially in Latin America should the disease spread to that continent. The lack of regional differences in CMD resistance among the improved genotypes indicate that resistance is durable.

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