Characterizing genotypic variation in biochemical composition, anti-nutritional and mineral bioavailability of some Nigerian yam (Dioscorea spp.) land races.

The aim of this study was to characterize 43 genotypes from five yam species [Dioscorea rotundata (Poir), Dioscorea alata (Linn), Dioscorea bulbifera (Linn), Dioscorea cayenensis (Lam) and Dioscorea dumetorum (Kunith) Pax] which are major land races in Nigeria in terms of their chemical composition, nutritional, anti-nutritional and mineral bioavailability. Findings showed that there was genotypic variation in terms of chemical composition, mineral profile and bioavailability of the minerals among the germplasm. D. bulbifera had the highest cell wall carbohydrates, (cellulose: 3.2%, hemicelluloses, 2.1%, lignin, 1.1%, acid detergent fibre (ADF) 3.2%, neutral detergent fibre (NDF) 6.4%), D. rotundata had the highest oxalate (606 mg/kg). In conclusion, intra and inter-species variations exist among the yam germplasm in terms of their chemical composition, anti-nutritional and mineral bioavailability. Phytate content of the yam genotypes did not affect the bioavailability of Zn but Ca was affected significantly. The Ox:Ca ratio in most of the yam varieties were below one, thus bioavailability of Ca in yam by oxalate is variety dependent.