Genetic dissection of grain nitrogen use efficiency and grain yield and their relationship in rice

Breeding for improved grain yield (GY) and grain nitrogen use efficiency (NUE) is an important objective of many rice breeding programs. A better understanding of the genetics of these two complex traits and their genetic relationship is required for more efficient breeding. This study reports the results of a linkage mapping study conducted for these two traits using 127 rice recombinant inbred lines (RILs) derived from the cross of Zhanshan 97/Minghui 63. Phenotypic data were collected under two nitrogen conditions in 2006 and 2007. For NUE, four and six QTLs were identified in 2006 and 2007, respectively. These QTLs were on chromosomes 1, 2, 6, 7 and 11. For GY, nine and five QTLs were detected on chromosomes 1, 2, 7 and 11 in 2006 and 2007, respectively. The phenotypic and genetic correlations between NUE and GY are positive and highly significant. Four genomic regions, including C86–C2340 on chromosome 1, RZ599–R1738 on chromosome 2, RZ471–C1023 on chromosome 7 and R3203–RM20a on chromosome 11, were found to contain QTLs for both NUE and GY. The effects of the co-located QTLs were in the same direction for NUE and GY, providing a genetic basis for the observed positive genetic correlation between the two traits. These genomic regions might be explored for the simultaneous improvement of NUE and GY in breeding.

► Significant positive phenotypic and genetic correlations are found between NUE and GY.
► C86–C2340 on chromosome 1, RZ599–R1738 on chromosome 2, RZ471–C1023 on chromosome 7 and R3203–RM20a on chromosome 11 were found to contain QTLs for both NUE and GY.
► The effects of the co-located QTLs are in the same direction for NUE and GY, which provide a genetic basis for the observed positive genetic correlation between the two traits.
► These four regions would be explored for simultaneous improvement of NUE and GY in breeding.