Genetic characterization of exotic and landraces of cassava in Ghana

Thumbnail Image
Journal Title
Journal ISSN
Volume Title
Cassava cultivars grown in Ghana are often misrepresented due to improper characterization of the genetic materials available. The genetic diversity of 45 accessions which consist of 24 exotic and 21 landraces (selected as a core of 150 cassava accessions) collected from Crops Research Institute of Ghana were assessed and characterized using agro-morphological and molecular means. Both quantitative and qualitative traits such as plant height, angle at first branching, canopy spread, petiole length, root yield, dry matter content, root shape, petiole colour, and pubescence on apical leaves were used to assess their variability for phenotypic characterization. Genomic DNA of the accessions were extracted and used as template for Polymerase Chain Reaction (PCR) amplification involving nine Simple Sequence Repeat (SSR) markers. The recorded gel bands as well as the agro-morphological traits were subjected to cluster analysis and development of dendrogram to show the corresponding similarity coefficients. Agro-morphological characterization grouped 2 accessions into cluster A, whilst 43 accessions were grouped in cluster B. Molecular characterization also grouped 16 accessions in cluster A and 29 in cluster B. Overall, both molecular and agro-morphological characteristics put 3 accessions in cluster A and 42 in cluster B. The genotype identification showed that, the phenotypic characters have a similarity coefficient range of 0.80%-1.00% whilst the molecular also had a wider coefficient range of 0.2-1.0%. These features showed the extent of diversity present in the accession evaluated and served as a basis for efficient management and utilization of germplasm in breeding programme. Therefore, the application of morphological descriptors in characterization of germplasm should be backed by the use of molecular markers.
A Thesis submitted to the School of Graduate Studies, Kwame Nkrumah University of Science and Technology, Kumasi, in partial fulfilment of the requirements for the Degree of Master of Science in Agronomy (Plant Breeding),