| Summary: | Sweetpotato [Ipoma batatas (L.) Lam.] is a major subsistence crop in Sub-Saharan Africa, where iron and zinc deficiency in humans is an important health problem. A sweetpotato cultivar suited for subsistence farming, with high iron and zinc concentration, would be important in alleviating these deficiencies.
The main objective of this research was to identify the extent of genetic variability of iron and zinc concentration in sweetpotato germplasm. An important subcomponent of this research was to determine the heritability of iron and zinc in sweetpotato. Protocol development studies were also conducted to aid in determining proper sampling technique.
The results of the protocol development study indicated there was a significant replication effect between plot replicates but that no significant variation existed among roots from a plant, among plants from a given replicate plot, or among different root zones. In general, most of the genetic variability present was attributable to the difference in genotype. Therefore, one root from each replicate is sufficient for determining iron and zinc concentration in sweetpotato.
A three-fold difference between high- and low-yielding cultivars for iron and zinc for ~80 cultivars was observed. The cultivars with the highest iron concentration were 'Kyukei No. 63' and 'Pata de Oso', both with ~7 ppm iron, fwb, from Japan and Peru, respectively. This compares with cultivars 'Pung-mi' and 'Chuquimanco' from Korea and Peru, respectively, both with ~3 ppm iron, fwb. These results suggest that sweetpotato with the highest levels of iron and zinc could provide about 30% and 15% of the daily dietary intact of these micronutrients, respectively. This is based on daily consumption of one 300-gram root. Iron and zinc in sweetpotato is highly available to humans given low phytic acid and high ascorbic acid concentration in orange flesh varieties.
The heritability study showed high broad-sense heritability for iron (H<sup>2</sup> = 0.74), zinc (H<sup>2</sup> = 0.82), and dry matter concentration (H<sup>2</sup> = 0.93) among half-sib families. These results and those which showed a positive correlation between iron and zinc concentration suggest that traditional breeding strategies like mass selection could improve the nutritional value of sweetpotato.
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