SLAF-Based Linkage Map Construction and QTL Mapping of Nitrogen Use Efficiency in Rice (Oryza sativa L.)

Rice production relies on large amounts of synthetic nitrogen fertilizer to meet crop nutritional demands. However, the current fertilizer use efficiency is poor, with an average of 30–50% of total applied nitrogen (N) recovered in grains. Consequently, optimizing N availability and N use efficiency (NUE) has become a major target for rice yield improvement, and looking for quantitative trait loci (QTL) associated with NUE can provide useful information for developing nitrogen efficient rice genotypes. The present study aims to identify QTLs associated with NUE and its two components, agronomic NUE (agNUE) and grain nitrogen increase rate (GIR). A recombinant inbred line population (RIL) derived from a cross between Nipponbare and OM052, consisting of 159 F3 individuals was developed and cultivated in low-N (8 kg N/0.67 ha, N8) and high-N (18 kg N/0.67 ha, N18) conditions. Specific length amplified fragment sequencing (SLAF) was used to genotype the RILs and construct a high-density linkage map spanning 1587.70 cM, consisting 2707 SLAF markers with an average interval of 0.59 cM between adjacent marker loci. QTL analysis confirmed four significant QTLs distributed among chromosome 1, 6, and 11, with the proportion of phenotypic variance explained by each QTL ranging from 2.96 to 11.11% and LOD scores from 1.67 to 3.75. Functional annotation of genes located within the QTL intervals revealed NUE putative candidate genes. Overall, the QTLs identified in this study contribute information that could be useful for NUE improvement in rice.