GENETIC AND BREEDING STRATEGIES FOR BIOFORTIFICATION AND NUTRITIONAL ENHANCEMENT IN HORTICULTURAL CROPS

Abstract

Micronutrient malnutrition continues to be a significant concern worldwide, as a large proportion of the population lacks sufficient quantities of one or more vital micronutrients through their regular diet. Horticultural commodities, particularly vegetables, fruits, roots and tubers, and spices, provide considerable potential for enhancing dietary nutrition and can serve as an important complement to biofortification programs targeting staple food crops. This review explores recent genetic, genomic, and biotechnological strategies employed to improve nutritional quality in horticultural crops. These approaches include conventional breeding, marker-assisted breeding, genomic selection, QTL analysis, genome-wide association studies, integrated multi-omics, and modern genome-editing technologies such as CRISPR/Cas9, CRISPR/Cas12, CRISPR/Cas13, base editing, and prime editing. The review focuses on the genetic and molecular mechanisms involved in the accumulation of major nutritional constituents, including provitamin A carotenoids, ascorbic acid, tocopherols, folates, iron, zinc, selenium, anthocyanins, flavonoids, phenolic compounds, proteins, and dietary fibre. The contribution of transcription factors, hormonal regulation, nutrient transporters, and metabolic pathways to nutrient biosynthesis and accumulation is considered across a wide range of horticultural crops, including tomato, potato, sweet potato, carrot, cassava, banana, citrus, apple, mango, Brassica vegetables, vegetable legumes, and spices. Although substantial advances have been achieved, improving nutritional quality remains complicated by undesirable effects on yield, genotype × environment interactions, fluctuations in trait expression under different growing conditions, and the presence of anti nutritional compounds that may restrict nutrient availability. The development of precise genome-editing technologies has opened new possibilities for simultaneously modifying several nutritional traits within the same genetic background. Nevertheless, the successful incorporation of these technologies into commercial horticultural production is influenced by regulatory requirements, biosafety considerations, consumer perceptions, and the overall performance of improved cultivars. Future nutritional breeding programs should therefore move beyond single-gene approaches and emphasize the integration of genomics, phenomics, multi-omics, and artificial intelligence-assisted breeding systems. Such integrated strategies can help address the complex genetic architecture of nutritional traits while simultaneously improving trait stability across environments and enhancing the bioavailability of nutrients.