European Journal of Sustainable Agroecosystems

Background: Nitrogen (N) is the major limiting nutrient in wheat (Triticum aestivum L.) production, but only 30-40% of applied nitrogen fertilizers is recovered from the harvested grains, resulting in significant economic losses as well as environmental damage due to nitrate leaching, ammonia volatilization and nitrous oxide emission. So it has become one of the objectives of modern wheat improvement programs to enhance nitrogen use efficiency (NUE) through genomics-based breeding. Objective: This review summarizes the last ten years of genomic and molecular studies related to NUE in wheat, placing together discoveries about quantitative trait loci (QTL), genome-wide association studies (GWAS), functional analysis of candidate genes, transcriptome profiling and genome editing. Literature source: A systematic search in Scopus, Web of Science, PubMed and Google Scholar (2015-2025) yielded 487 non-duplicate papers and 50 studies with the characteristics of interest that allowed finding and summarizing 38 papers for the thematic synthesis, apart from information obtained from the reports of the Food and Agriculture Organization (FAO) and the International Nitrogen Initiative. Main results: The literature examined reaches a consensus regarding numerous common regions of the genome and gene families that control the processes of nitrogen uptake (such as TaNRT1/TaNRT2, TaAMT), nitrogen assimilation (for example, glutamine synthetase/glutamate synthase, or GS/GOGAT), nitrogen remobilization (the NAC transcription factor NAM-B1/Gpc-B1 and its homologues), and nitrogen signal propagation (NIN-like proteins, bZIP, Dof transcription factors). Studies based on GWAS with the help of the SNP arrays had identified plenty of QTLs for NUE traits. At least some QTLs were shown co-localized in articles of different authors. Research gaps: The existing gaps are still persistent which include a limited cross-environment validation of GWAS loci, under-representation of phenotyping of plant root system architecture, poor integration of multiple omics data sets, and a reduced number of studies in smallholder farmers in South Asia and sub-Saharan Africa. Conclusion: Genomic knowledge has contributed significantly to the understanding of the mechanism of wheat NUE but effective utilization of genomic knowledge requires further multi-location validation, integration of multiple omics, and precision genome editing techniques.