Variations in genotype- and position-dependent seed tuber sprouting linked to skin morphology in white Guinea yam.

White Guinea yam (Dioscorea rotundata) is a staple tuber crop in West Africa; however, its vegetative propagation is constrained by irregular dormancy and unpredictable sprouting, which reduce planting efficiency and yield stability. This study examined how tuber skin and cortex morphology influence sprouting across 20 D. rotundata genotypes selected from an F₁ cross-population with a relatively uniform genetic background. Tubers were divided into head, middle, and tail parts to evaluate positional effects. Periderm thickness, cortex thickness, skin hardness, and surface roughness (fractal dimension) were quantified, and sprouting was assessed under screenhouse conditions. Analysis of variance showed that genotype and tuber position accounted for 30% and 20% of the total variation in sprouting time, respectively. Head sections had thinner periderm and generally sprouted earlier than middle or tail sections. Regression analysis indicated that thinner periderm and higher fractal dimension were associated with earlier sprouting, whereas greater skin hardness was associated with delayed emergence; cortex thickness showed inconsistent effects across tuber positions. These morphological traits explained 10–25% of the variation in sprouting time, indicating that additional physiological and genetic factors dominate sprouting responses. Overall, tuber skin morphology exerts a minor yet measurable influence on dormancy breaking and early sprouting in D. rotundata. Practically, our results suggest that selecting planting materials from head positions and using periderm thickness and surface texture as screening traits can help reduce sprouting variability and improve establishment, providing actionable targets for breeding and seed-yam management aimed at more uniform sprouting and efficient seed-yam production.