Genetic variability among different genotypes for root yield component characteristics was studied in Guinea Savannah Agroecological zones of Niger state to determine its effect on early root bulkiness. Sixteen parameters were evaluated in 420m2 at spacing of 1mx1m in a randomized complete block design in three replicates. Cassava genotypes were evaluated at 3 and 6 MAP (Month After Planting) to evaluate root bulkiness. REML/BLUP showed significant difference among genotypes for different harvesting periods for Harvest Index and fresh storage root yield (FSRY). Estimates of genetic variance for phenotypic (PCV) and genotypic coefficient of variation (GCV) were very close. PCV estimates were higher than GCV and varied from 39% to 13% for root weight and root size respectively. Broad sense heritability estimates were high for FSRY and ranged from 81% to 8% among root yield components. GCV estimates was higher for harvest index (34%) and least for number harvested (6.15%).

Keywords : Genetic Variability, Root Bulkiness, Heritability.