Implementing Marker-Assisted Selection for Biofortification of Staple Crops With Iron, Zinc, and Provitamin A: A Review
Micronutrient malnutrition remains a major global nutrition problem, particularly in populations whose diets depend heavily on staple crops. Iron (Fe), zinc (Zn), and vitamin A deficiencies can adversely affect growth, immunity, cognitive development, and overall health. Crop biofortification provides a sustainable breeding-based strategy for increasing the concentration of essential nutrients in commonly consumed foods. This review examines the application of marker-assisted selection (MAS) in the development of Fe-, Zn-, and provitamin A (PVA)-rich staple crops. Relevant peer-reviewed literature, scientific reviews, and institutional publications were examined using major academic databases and search platforms, including PubMed, Scopus, Web of Science, and Google Scholar. Particular attention was given to the genetic basis of micronutrient accumulation, molecular markers, marker-assisted backcrossing, marker-assisted recurrent selection, gene pyramiding, and recent applications in maize, rice, wheat, pearl millet, cassava, and other staple crops. Evidence from breeding programs indicates that MAS can improve the efficiency of selecting favorable alleles and can facilitate the introgression and combination of nutrient-associated genes and quantitative trait loci (QTLs). Major targets include crtRB1 and lcyE for PVA accumulation in maize, genomic regions associated with grain Fe and Zn in cereals, and nutrient-related loci in rice and cassava. Nevertheless, the effectiveness of MAS can be constrained by the quantitative inheritance of micronutrient traits, genotype × environment interactions, marker–gene recombination, limited genomic resources in some crops, and differences in nutrient bioavailability. Future breeding strategies should integrate MAS with genomic selection, high-throughput phenotyping, speed breeding, gene editing, and climate-resilient breeding. Overall, MAS represents an important component of modern biofortification programs and can contribute to the development of nutritionally improved, productive, and farmer-acceptable staple crop varieties.