GENETIC DIVERSITY ANALYSIS AND NUTRITIONAL ASSESSMENT OF COCOYAM GENOTYPES IN MALAWI

• Main Author: Mwenye, Obed John
• Other Authors: Dr IRM Benesi
• Format: Others
• Language: en-uk
• Published: University of the Free State 2010
• Subjects: Plant Sciences
• Online Access: http://etd.uovs.ac.za//theses/available/etd-09202010-120619/restricted/

Cocoyam (C. esculenta (L.) Schott and X. sagittifolium (L.) Schott) belongs to the family Araceae. Cocoyam has the potential to contribute significantly to world agriculture in terms of food, nutrition and crop diversification. Despite this the crop remains neglected in terms of research focus. Limited or no information exists on the prevalence, preference and utilisation as well as the pattern and level of diversity that exists in cocoyam germplasm found in Malawi. This study determined the level and pattern of genetic diversity of cocoyam from Malawi using ethno-botany, morphological characters and AFLP markers. Mineral composition of selected genotypes was also determined. The ethno-botanical survey showed that farmers in Malawi maintain a large amount of cocoyam germplasm. These farmers have rich ethno-botanical and ecological knowledge of the cocoyam cultivars they conserve. Farmerâs preferences regarding cocoyam cultivars included uses of plant parts, adaptation and eating quality. Morphological characters showed high levels of variation among accessions. Two main species of cocoyam, Colocasia and Xanthosoma were identified based on leaf base shapes (petiole attachment). AFLP markers showed low levels of genetic diversity between accessions as opposed to the high morphological diversity. A combined (morphological characters and AFLP data) analysis using UPGMA clustering, PCA and AMOVA further alluded to the presence of the two cocoyam species within the germplasm. High levels of variation were detected between the two species and low levels of variation were observed within each of the two species (Colocasia and Xanthosoma). The PCA exhibited a better representation of the genetic diversity pattern than the hierarchical clustering. Accessions showed high levels of mineral composition. Potassium was identified as the major mineral component. Accessions also exhibited high levels of essential minerals (Ca, Fe and Zn). Incorporating cocoyam into the diet of the resource poor farmers could help in the fight of the most prevalent micro-nutrient deficiencies. A study on morphological and genetic diversity as well full nutritional assessment of the tubers and leaves of cocoyam from the whole country is recommended. In order to broaden the narrow genetic base observed importation of foreign material is recommended.