Using marker assisted selection to hasten screening of cassava cultivars developed through introgression of cassava mosaic disease (CMD) resistance into cassava landraces in Ghana.

2011

English

Cassava mosaic disease (CMD), the most important disease of cassava (Manihot esculenta Crantz) is a potential threat to Africa's cassava production. The disease is embedded 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 (TME11) from International Institute of Tropical Agriculture (IITA). The resultant progenies found to have a reasonable level of resistance (score, 1-3) to the CMD were AW 18, 273 Nyamebekyere, 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 resistant cultivar. The backcross one (BC1) progenies totaling 224 were screened with molecular markers that are associated to the CMD 2 gene. De-oxyribonucleic Acid (DNA) was extracted from leaves of the 224 BC1 progenies and 13 parents. Two Simple Sequence Repeats (SSR) markers (SSY28 and NS158) and one Sequenced Characterized Amplified Region (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 CMD2 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 for yield and starch cooking quality in future breeding work.

Ribeiro, P. F.; Ankromah, R.; Manu-Aduening, J.