Genotypic differences in grain yield, and nitrogen absorption and utilization in recombinant inbred lines of rice under hydroponic culture

To examine the possibility of breeding higher-yielding cultivars with a high nitrogen use efficiency (NUE) and to provide simple criteria for the selection and breeding of high-yielding cultivars with a high NUE and useful information for the mapping of quantitative trait loci (QTL) controlling NUE, recombinant inbred lines (RILs) of rice were subjected to hydroponic culture in 2000 and 2001. Grain yield and yield components, total nitrogen absorption (NTA), pre-heading and post-heading nitrogen absorption (pre-NA and post-NA, respectively), and nitrogen use efficiency for grain yield (NUEg) were analyzed. Transgressive segregations for grain yield and yield components, NTA and NUEg were observed. RILs with a high grain yield tended to show a larger number of panicles m(-2) and of spikelets per panicle, and a higher filled grain percentage than RILs with a low grain yield. Increasing NTA and NUEg resulted in increases in the number of spikelets m(-2) and grain yield, while increasing NTA resulted in a decrease in NUEg. The contribution ratio of the number of panicles m(-2) to grain yield was higher than that of the other yield components in both 2000 (31.8%) and 2001 (32.2%). In both years, the relative contribution ratios of NUEg and NTA to grain yield were approximately 56% and 43%, respectively. At the same high-yielding level, there was a significant difference in the NTA and NUEg values. These results suggest the possibility of breeding high-yielding cultivars with higher NUEg.