Yield Evaluation and Morphological Variability of Tubers of Intra-Specific Hybrids of Dioscorea Rotundata

Abstract

The study was conducted to evaluate fifteen hybrid yam genotypes at the last stage of Uniform Yield trial (UYT) developed through intra-specific crosses with three landraces of Dioscorea rotundata. The objectives were to determine the variability in tuber dry matter yield of the genotypes, good tuber shape, tuber surface skin texture and tuber morphological variations. The experimental design was a two factorial arrangement in a Randomized Complete Block Design. The results showed high significant (P<0.01) genotype variation in fresh tuber yield, Tuber dry matter yield and number of tubers indicating substantial variation among the yam genotypes except for tuber shape index and days to physiological maturity of the tubers. Insignificant (P>0.05) year effect was observed for number of tubers, tuber dry matter yield, fresh tuber yield and tuber shape index indicating non- differential performances of the genotypes at different years. The morphological characterization of the yam tubers using yam manual descriptor code character and mathematics of information theory which allows simultaneous analysis of both quantitative and qualitative data indicated that the yam tubers produced by the yam genotypes were distinctively differentiated from each other showing evidence of varietal variation resulting from segregation during cross pollination. Also, the result indicated strong significant (P<0.01) variation on the effect of year x genotype interaction. This implied differential performances of varieties at different years. Based on this study, the following yam genotypes were selected using 5% selection pressure as superior in tuber dry matter yield potential in both years: UYT/05/085, UYT/05/070, UYT/05/001, UYT/05/048, UYT/05/044 and UYT/05/052. These genotypes had good shape and three of the genotypes had tuber skin surface texture that appeals to the eye. These could be selected for commercial yam production and should be included in the germplasm for further breeding purposes.