Yam is a popular tuber crop in Nigeria, contributing to food security and income of farmers. Research on yam improvement has been very slow due to insufficient information on genetic diversity of the crop. The objectives of this study are to identify, characterize and classify some Dioscorea species of yam in farmers' field in Nigeria using morphological and isozyme indicators. Twenty-eight genotypes of yam (Dioscorea) species comprising IITA elites, local landraces and adaptable farmers'

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... ies were planted at a space of 1m x 1m in a randomized complete block design in two replications. Two major morphological clusters were observed. Cluster I comprised relative species (D. dumetorum, D. abyssica and D. schimperana) with D. alata (water yam) and cluster II was dominated by D. rotundata and D. cayenesis. High correlation between morphological and molecular data analyses were observed in this study. Three isozyme markers were observed as good discriminant for yam: SKDH, 6-PGD and AAT. Isozyme markers analysis indicated that D. alata species were distantly related to D. rotundata and D. cayenesis, while D. rotundata species were closely related to D. cayenesis. The study provided important information for breeders which could be exploited for the development and improvement of the yam crop.