Genetic diversity of sweet yam “Dioscorea dumetorum “(Kunth) Pax revealed by morphological traits in two agro-ecological zones of Cameroon

Genetic diversity of 43 Dioscorea dumetorum accessions and two of Dioscorea cayenensis Lam as out-group species was evaluated for qualitative and quantitative traits in two different agro-climatic zones Baham (05°20.040' N/010°22.572’ E and 1634±3 masl, agro-ecological zone III with rainfall of 1500 to 2000 mm, and mean annual temperature of 19°C) and Ekona (04°12.773'N/009°19.425'E and 445±3 masl, agro-ecological zone IV with rainfall of 2500 to 4000 mm and mean annual temperature of 26°C). Forty one (41) morphological characters according to International Plant Genetic Resources Institute (IPGRI) descriptor, including nine quantitative and 32 qualitative characters were analyzed for multivariate analysis using cluster analysis, principal component analysis (PCA), and analysis of variance. For quantitative characters, cluster analysis revealed three major clusters. The first three components with eigen values > 1 contributed 83% of the variability. The PCA results indicate that traits which largely contributed to the variability within and between the accessions were stem length, leaf length, internode number, leaf width, harvest index, leaf number and internode length. Traits such as harvest index, internode number and stem length showed high heritability and high genetic advance. For qualitative traits, cluster and principal component analysis revealed two major clusters in Baham as well as in Ekona. The traits such as spines on stem base, spines on stem above base, spines length contributed to the variability within and between the accessions. However, the limits of morphological characters in the study of diversity have been detected. Key words: Dioscorea dumetorum, morphological traits, characterization, agro-climatic zone, Cameroon