Heritability analysis of putative drought adaptation traits in sweetpotato.

Abstract

Drought stress is a constraint to sweetpotato (Ipomoea batatas L. (Lam)) production in many parts of Sub- Saharan Africa. In this region, crop farming is predominantly rain fed; therefore, breeding for drought tolerance is appropriate for addressing low sweetpotato productivity since the crop is largely produced by resourcelimited farmers. As part of developing drought tolerant genotypes in Uganda, this study aimed at determining the nature of genetic control and heritability associated with selected drought adaptation traits. Ten randomly chosen clones from each family were evaluated for three traits; tuber yield, crop vigour and canopy cover as well as five traits (leaf senescence, leaf rolling, leaf retention, SPAD readings and root vertical pulling) at 80% field capacity and under no watering conditions for three weeks in a glasshouse. Diallel analysis revealed significant effects for both GCA and SCA, indicating both additive and non-additive gene actions were present. Baker’s ratio was large in most traits (>0.50), indicating predominance of additive effects. Heritability coefficients were high in most traits (>0.50), indicating that genetic gains can be achieved by conventional breeding. The predominance of additive genetic control realised in this study implies that use of small numbers of parents with suitable GCA effects is most appropriate for drought tolerance improvement in sweetpotato.

Key Words: Combining ability, diallel, Ipomoea batatas