N-efficiency character of high-yield rice is not affected by soil nitrogen supply level

Low fertilizer nitrogen efficiency and high fertilizer input in agriculture cause serious environmental pollution and waste of fertilizers. In order to select nitrogen-efficient cultivars, field experiments were conducted with 199 rice (Oryza sativa L., japonica) cultivars/lines at three nitrogen levels (0, 126 and 180 kg N/ha) in order to screen the differences of genotypes in nitrogen efficiency. Results showed that genotype is the dominating factor in determining grain yield rather than environmental factors. In general, grain yield relies on: 1) nitrogen uptake and biomass; 2) grain nitrogen use efficiency and physiological nitrogen use efficiency; and 3) harvest index and nitrogen harvest index. The N-efficient cultivars are LA19, XS48, MJ199, YJ38, HD and GD4, and N-inefficient cultivars are DN413, HJ19, FNXHM, NY1819 and ELIO. Our results demonstrated that nitrogen use efficiency is a genetic character of these cultivars, and those selected N-efficient cultivars may be applied in agricultural systems with low nitrogen input and still produce high yield. These cultivars are therefore ideal plants for studying the genetic and molecular mechanisms of nitrogen use efficiency.