Genetics of carotenoids for provitamin A biofortification in tropical-adapted maize

Yellow maize contains high levels of β-carotene (βC), making it an important crop for combating vitamin A deficiency through biofortification. In this study, nine maize inbred lines were selected at random from 31 provitamin A (PVA) maize inbred lines and crossed in a partial diallel mating design to develop 36 crosses. The crosses were evaluated in the field in two locations (Samaru and Kerawa) and their seed carotenoid content were determined by high-performance liquid chromatography. The modes of gene action, heritability, and correlations between agronomic traits and carotenoid content were estimated. Additive genetic variances (σ2a) were lower than non-additive genetic variances (σ2d) for all the carotenoids, plant height (PH), and grain yield (GY), suggesting a preponderance of non-additive gene action. Broad-sense heritability (H2) was high (H2 > 60%) for zeaxanthin, days to anthesis, and PH, moderate (30% < H2 < 60%) for lutein and GY, and low (H2 < 30%) for alpha carotene, beta cryptoxanthin, βC, and PVA. Genetic advance as a percentage of mean, considered with H2, also suggests a preponderance of non-additive gene action for PVA carotenoids. Hybrid variety development is thus an appropriate approach to improving grain yield and PVA. GY showed no significant genotypic correlations with carotenoid content, suggesting that these traits can be improved concurrently. Thus, there is ample scope for improvement of PVA and GY in the sample of tropical-adapted maize.