Improving nitrogen use efficiency (NUE) is essential for sustainable wheat production, given the global demand for high-yielding and environmentally resilient crop varieties. NUE is a complex trait governed by multiple genetic, physiological, and environmental factors. This review synthesizes recent advances in the genetic dissection of NUE in wheat, focusing on quantitative trait loci (QTL) mapping, genome-wide association studies (GWAS), and transcriptome analyses. Furthermore, novel approaches such as protein turnover quantification, epigenetic regulation, NIR-based quality prediction, and genomic selection optimization are discussed as emerging strategies to enhance NUE. Key genes identified include nitrate transporters (NRT1, NRT2), nitrogen assimilation enzymes (GS, GOGAT), transcription factors (NLPs, WRKYs, NACs), and signal transduction components (SnRK, CIPK). Integrative studies combining genomics, transcriptomics, and machine learning offer new insights into the dynamic regulation of NUE. This review highlights the importance of multi-layered breeding approaches and provides valuable genetic resources and methodological frameworks for future wheat NUE improvement programs.

Breeding wheat cultivars with high nitrogen use efficiency is crucial for sustainable agriculture. In this study, 130 durum wheat accessions from 53 countries were cultivated under two nitrogen fertilization levels to investigate variations in agronomic traits and identify accessions suitable for low-nitrogen conditions. Under no nitrogen fertilization, SPAD value (-99.2), flag leaf length (−15.8 mm), grain area (−0.52 mm²), grain length (−0.27 mm), thousand-grain weight (+5.2 g), and grain protein content (−4.2%) showed significant differences compared to that under standard nitrogen fertilization. Among these traits, the SPAD value exhibited a strong positive correlation with protein content in the absence of nitrogen fertilization, suggesting its potential as an indicator for selecting germplasm with superior nitrogen use efficiency. Hierarchical cluster analysis, based on the differences in the six traits under the two nitrogen fertilization levels, classified the 130 durum wheat accessions into three groups (Groups 1, 2, and 3). Accessions in Group 2 exhibited superior adaptability under no nitrogen fertilization compared with those in the other two groups. We identified seven accessions in Group 2 that exhibited minimal decreases in SPAD values and protein content under no nitrogen fertilization for use in wheat breeding programs aimed at developing cultivars with high nitrogen use efficiencies.

The rice cultivar ‘Namchan’ was developed to achieve high yields under low-nitrogen fertilizer conditions and enhance cultivation stability. ‘Namchan’ was derived from a cross between ‘Nikomaru’, a Japanese rice cultivar known for its excellent ripening ability in high-temperature conditions, and ‘Saenuri’, a Korean mega rice cultivar renowned for its high cultivation stability. To shorten the breeding period, anther culture was applied to F1 plants. ‘Namchan’ was selected through the pedigree method, yield trials, and local adaptability tests, with high selection pressure for ripening ability and cultivation stability. The heading date of ‘Namchan’ was August 16, four days later than that of ‘Nampyeong’. ‘Namchan’ exhibited strong tolerance to lodging and preharvest sprouting, indicating high cultivation stability. Despite having more grains and panicles compared to that in ‘Nampyeong’, ‘Namchan’ exhibited excellent ripening ability, presumed to be inherited from ‘Nikomaru’. ‘Namchan’ showed intermediate resistance to rice blast and resistance to bacterial blight and rice stripe virus. ‘Namchan’ had excellent grain appearance, improved milling performance, and superior taste compared to ‘Nampyeong’. ‘Namchan’ exhibited a yield of 6.34 MT/ha under normal nitrogen fertilizer conditions, and its index at 115%, when compared to that of ‘Nampyeong’, is the highest among Korean japonica rice varieties. It exhibited a high yield of 5.45 MT/ha even under low-nitrogen fertilizer conditions. ‘Namchan’ is promising as an outstanding cultivar that can contribute to carbon neutrality through the reduction of nitrogen fertilizers and greenhouse gases (Registration No. 8134).

The
objective
of this study is to assess the impacts of additional N fertilization on agricultural traits, flour characteristics, and noodle quality of O-free, a variety known for reduced allergy effects. With increasing fertilization rates, both culm length and spike length showed an increase, accompanied by a rise in grain nitrogen removal due to higher protein content in the grains. The leaf area index (LAI) reached its peak during the booting stage, while the canopy LAI peaked at 21 days after flowering (21-DAF). Although LAI of plant was higher in the treatments with additional nitrogen (N1 and N2) compared to the control (N0), there was no significant difference observed in canopy LAI. Chlorophyll fluorescence values were highest at 21-DAF and lowest at 35-DAF, regardless of the fertilizer rate. The dry weight of leaves and stems was highest at 7-DAF in N0 and N1 treatments, but at 21-DAF in N2 treatment. During grain filling, the nitrogen content decreased in leaves and stems, while it increased in the grains. With higher fertilization rates, there was an increase in the moisture content, flour color value, protein content, and sedimentation value of flour, whereas the particle size of flour decreased. Dough extensibility, mixing time, and protein strength showed an increase as the fertilizer rate increased, but dough stability decreased. The control exhibited the highest starch gel stability and aging, while N1 had the lowest starch swelling. Cooked noodles demonstrated increased brightness, thickness, and hardness with increasing fertilizer rate, but elasticity and viscosity showed no significant changes.