Nitrogen Use Efficiency in Rice under Abiotic Stress: Plant Breeding Approach

Nitrogenous fertilizer has remarkably improved rice (Oryza sativa L.) yield across the world since its discovery by Haber-Bosch process. Due to climate change, future rice production will likely experience a wide range of environmental plasticity. Nitrogen use efficiency (NUE) is an important trait to confer adaptability across various abiotic stresses such as flooding, drought and salinity. The problem with the increased N application often leads to a reduction in NUE. New solutions are needed to simultaneously increase yield and maximize the NUE of rice. Despite the differences among flooding, salinity and drought, these three abiotic stresses lead to similar responses in rice plants. To develop abiotic stress tolerant rice varieties, speed breeding seems a plausible novel approach. Approximately 22 single quantitative trait loci (QTLs) and 58 pairs of epistatic QTLs are known to be closely associated with NUE in rice. The QTLs/genes for submergence (SUB1A) tolerance, anaerobic germination (AG, TPP7) potential and deepwater flooding tolerance (SK1, SK2) are identified. Furthermore, phytochrome-interacting factor-like14 (OsPIL14), or loss of function of the slender rice1 (SLR1) genes enhance salinity tolerance in rice seedlings. This review updates our understanding of the molecular mechanisms of abiotic stress tolerance and discusses possible approaches for developing N-efficient rice variety.