Enhancing nitrogen use efficiency in cereal crops: from agronomy to genomic perspectives

Cereal crops are the most important grain crops and are extensively cultivated around the world due to their nutritional value, fodder, and biofuel production. The significant increase in cereal grain yield is primarily attributed to the application of inorganic nitrogenous fertilizer. But the inefficient utilization of the fertilizer leads to leftover N, which has a negative impact on human health and the environment. Hence, a pressing priority is to enhance nitrogen use efficiency (NUE) in crop cultivation through improved management practices. Additionally, it is important to assess how NUE interacts with the plant characteristics. NUE depends on the absorption and distribution of nitrogen through enhanced root architecture and transporters, processing, and remobilization within storage organs. Moreover, NUE is determined by N distribution across roots, stems, leaves, grains, photosynthetic capacity, and leaf senescence. Information on the scope of exploitable genetic variability and their genetic control is needed to increase NUE through genetic modifications. In this review, we provide an integrated approach that combines agronomy, physiology, genetics, and genomics for a comprehensive understanding of the critical components involved in NUE. This understanding is crucial for developing crop management practices and identifying promising key genetic factors to improve NUE in cereals.