Using Marker Assisted Selection Technique as A Tool to Identify Cassava Mosaic Disease Resistant Cultivars in First- Backcross Populations
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Date
April, 2010
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Abstract
Cassava Mosaic Disease (CMD), the most important disease of cassava (Manihot esculenta) is a potential threat to Ghana’s cassava production. The disease is implanted in most landraces resulting in low yields. Host plant resistance has been found to be the best control strategy. A breeding programme using genetic hybridisation and Marker Assisted Selection was initiated in 2007 to improve the resistance levels of farmer-preferred landraces and reduce the long breeding cycle for developing improved cassava varieties. Thirty farmer-preferred landraces were selected and crossed with a high yielding and mosaic resistant cultivar, TME 11, from IITA. The resultant progenies found to have a level of resistance to the CMD were AW 18, Nyamebekyere 273, NK 43, AW 3, NK 26, K 25, Dabodabo, Ahwengyankwa, 674 Debor, Degarti, Agric Bankye, and NK 57. These resultant progenies were backcrossed to the recurrent parent. The backcrossed one (BC1) progenies totalling 224 were screened with molecular markers that are associated to the CMD 2 gene. DNA was extracted from leaves of the 224 BC1 progenies and 13 parents. Two SSR markers (SSR 28 and NS 158) and one SCAR marker RME1 were used to screen and select for the resistant BC1 progenies. Marker Assisted Selection (MAS) revealed that 82% of the genotypes had at least a marker allele for the CMD 2 gene, indicating resistance. The study further revealed that by using MAS, the breeding cycle of cassava in the generation of varieties could be reduced from 8 years to 2 years. The resistant genotypes identified will be evaluated in future breeding work.
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A Thesis submitted to the Department of Crop and Soil Sciences, Kwame Nkrumah University of Science and Technology in Partial Fulfilment of the Requirements for the Degree Of MASTER OF SCIENCE, Faculty of Agriculture.