Genetic improvement toward nitrogen-use efficiency in rice: Lessons and perspectives

The indispensable role of nitrogen fertilizer in ensuring world food security together with the severe threats it poses to the ecosystem makes the usage of nitrogen fertilizer a major challenge for sustainable agriculture. Genetic improvement of crops with high nitrogen-use efficiency (NUE) is one of the most feasible solutions for tackling this challenge. In the last two decades, extensive efforts toward dissecting the variation of NUE-related traits and the underlying genetic basis in different germplasms have been made, and a series of achievements have been obtained in crops, especially in rice. Here, we summarize the approaches used for genetic dissection of NUE and the functions of the causal genes in modulating NUE as well as their applications in NUE improvement in rice. Strategies for exploring the variants controlling NUE and breeding future crops with "less-input-more-output" for sustainable agriculture are also proposed.