Biological Determinants of Crop Nitrogen Use Efficiency and Biotechnological Avenues for Improvement

Crop nitrogen use efficiency (NUE) is crucial for sustainable food security as well as for a sustainable environment. It can be improved in the short term through improved fertilizer formulations and cropping practices under integrated nutrient management, but the inherent capacity of the plant to take up, retain and use the available nitrogen (N) has to be tackled biologically. The last decade has witnessed several major advances in our understanding on the biological determinants of N-response and N-use efficiency, which are opening up biotechnological opportunities for improvement in the medium to long term. This chapter highlights the various biological determinants including the uptake and assimilation of external N, remobilization of internal N, efflux or loss of N from plants. The emerging opportunities for NUE enhancement span a vast array of approaches including germplasm diversity, root architecture, molecular markers, phenomics, genomics and functional genomics, metabolomics and micro-Ribonucleic Acids (miRNAs). They are amenable to both transgenic, as well as non-transgenic selection/breeding options.