Molecular tools complementing conventional breeding approaches in vegetable crops: A critical review

Vegetable crops constitute an essential component of global food and nutritional security by providing vital vitamins, minerals, antioxidants and dietary fibre essential for maintaining human health and preventing nutritional deficiencies. With rapid demographic growth, accelerated urbanisation and climate-induced environmental fluctuations, the demand for high-yielding, resilient and nutritionally dense vegetable cultivars have increased substantially. However, vegetable production faces pervasive constraints, including devastating biotic pressures (fungi, bacteria, viruses, insect pests and nematodes) alongside abiotic stresses such as drought, extreme temperatures, salinity and water scarcity. Conventional breeding approaches have laid the cornerstone of vegetable improvement through recurrent selection, hybridisation and wide backcrossing. Nonetheless, empirical reliance on phenotypic evaluation renders conventional selection labour-intensive, time-consuming and prone to environmental noise, particularly for polygenic traits governed by complex genetic architectures and high genotype × environment interactions. The advent of molecular tools has revolutionised vegetable breeding by enabling accurate, genotype-based selection at the DNA level. This review provides a comprehensive critical synthesis of molecular technologies complementing conventional vegetable breeding, spanning diagnostic molecular markers, high-density quantitative trait locus mapping (QTL) mapping, marker-assisted backcrossing and multi-gene pyramiding across solanaceous, cucurbitaceous and cruciferous crops. Furthermore, this review addresses the cutting-edge innovations of the genomic era, including whole-genome resequencing, pangenomics, haplotype-led breeding, speed breeding protocols, doubled haploid technology, multi-omics integration, clustered regularly interspaced short palindromic repeats (CRISPR)-Cas genome editing and artificial intelligence-driven digital phenotyping. Current methodological bottlenecks, epigenetic nuances and synthetic biology avenues are critically evaluated to outline an agile roadmap for climate-resilient and biofortified vegetable development.