2008 年 58 巻 2 号 p. 113-120
In rice (Oryza sativa L.) plants, accumulation and remobilization of nitrogen (N) are essential physiological processes that determine grain yield and quality. The objectives of the present study were to identify and characterize the genomic regions associated with this N dynamics by quantitative trait locus (QTL) analysis. In the present study, 191 recombinant inbred lines (F7) derived from a cross between Milyang 23 (Indica-type) and Akihikari (Japonica-type) were repeatedly evaluated for leaf nitrogen (N) concentration throughout four cropping seasons in Joetsu, Japan and Los Baños, Philippines, to perform interval mappings using a 182 RFLP marker-based linkage map. The locations and effects of the QTLs detected showed that the N dynamics was controlled by 15 genomic regions classifed into three groups. Four regions in Group I (chromosomes 1, 2, 7 and 8) affected only the N concentration before heading, i.e., N accumulation during the vegetative phase; whereas eight regions in Group II (chromosomes 2, 3, 4, 6, 7, 9, 10 and 12) affected the N concentration after heading, i.e., N remobilization during the reproductive phase. Only three regions (chromosomes 1, 2 and 10) in Group III exerted effects on both N concentrations in the vegetative and reproductive phases. In 12 of these 15 regions, expression of the QTLs depended on the cropping seasons and sites. Statistical tests enabled to detect significant genotype × stage and genotype × season interaction effects for nine and eight regions, respectively. Characterization of the 15 regions demonstrated that the genetic control of N dynamics involves a number of genes whose effects were enhanced or suppressed by plant ontogeny and the growth environment.
