Characterization of nutrient use-efficient genotypes of Dioscorea Alata and Dioscorea Rotundata using phenotypic traits, SSR markers and farmer participatory approach.

The overall objective of this study was to identify nutrient use-efficient varieties of yam genotypes from the IITA and farmer local varieties from the Northern Region of Ghana. Both laboratory analysis and farmer description indicated low soil fertility in the study area, hence the need for nutrient use-efficient yam genotypes. In all, 45 genotypes made up of 20 D. alata and 21 D. rotundata from IITA – Ibadan with four local genotypes from farmers were evaluated in Randomized Complete Block Design (RCBD) across the three districts of the Northern Region of Ghana. A total of 20 quantitative traits and 29 qualitative traits of the farmer were used to evaluate the genotypes. The data taken ranged from sprouting to tuber maturity. Quantitative data were subjected to descriptive statistics, principal component analysis, correlation matrix and Hierachial cluster analysis using Euclidean distance coefficients. The analysis revealed that, the 20 quantitative variables and 29 qualitative farmer traits were grouped into several components in which the first six axes explained 82.70% in D. alata and 82.42 in D. rotundata of the total variation. In all, six quantitative traits (Leaf area, Leaf surface area, high chlorophyll content at the lower to the middle leaves, number and weight of seed yam, ware yam and total yam) revealed the highest variability and therefore, were considered as very significant to be used to characterize nutrient use-efficient genotypes for both yam genotypes. However, qualitative information on insect pest and disease score indicated no to very low symptoms. Farmer criteria used for characterization include; medium to large leaves, medium to large canopies, smooth to slightly rough leaves with no infestation of insect pest and disease infection. Besides, high yielding, big/long tubers, smooth with few to no hairy tuber surface, no insect pest infestation and disease infection, long shelf life with high proportion of ware and seed yam productions determined farmer preferred nutrient use-efficient genotypes. The selection of the high performing genotypes was as a result of the significant variation among genotypes using the phenotypic and farmer criteria. The use of the cluster analysis separated these genotypes into numerous clusters with similar traits. The genetic diversity conducted using seven SSRs markers to determine high performance genotypes in both species revealed a total allele number of 23 and 27 with 3.28 and 3.85 allele per loci in D. alata and D. rotundata, respectively. Mean genetic diversity recorded was 0.53 and 0.42 with polymorphic information content (PIC) found to have a mean value of 0.37 and 0.49 in D. alata and D. rotundata, respectively, showing a low level of polymorphism detected by the primers. A greater amount of dissimilarities of 0.62 to 1.00 in both species was revealed using the molecular cluster analysis based on Unweighted Pair-Group Mean Average (UPGMA). At a dissimilarity coefficient of 0.175 (17.5%) and 0.25 or (25%), the dendrogram identified two main clusters with six sub-clusters for D. alata and six main clusters for D. rotundata respectively. The study has revealed that, the use of morphological characters and farmer perception identified TDr 00/00951, TDr 09/00001, TDr 95/18988, TDr 95/19177 and Larbako as well as TDa 98/01168, TDa 09/00228, TDa 02/00012, TDa 98/01174, TDa, 92-2 and Seidubile as D. rotundata and D. alata nutrient use-efficient genotypes respectively. Besides, results from marker assisted selection, revealed that, diversity among genotypes are very high. This enhances selection of high yielding genotypes in low fertility soil for advance breeding and hybridization programmes.

Source: KNUST