Linkage Analysis of QTL on Chromosome 8 Controlling Nitrogen Utilization under Low NH₄⁺ Concentration in Rice (Oryza sative L.)

Abstract

Nitrogen utilization is regulated by many factors at various steps. Root elongation is stimulated under low nitrogen concentration in rice. Preliminary study showed that a QTL controlling root length under low NH₄⁺ concentration was detected on the long arm of chromosome 8. A CSSL, SL-225, has a Kasalath segment on a long arm of chromosome 8 in Koshihikari genetic background. To characterize QTL under various NH₄⁺ concentrations, the germinated SL-225 and Koshihikari were hydroponically grown under 5, 25, 50 or 500 μM NH₄⁺ during 9 days. Only under 5 μM NH₄⁺ concentration, root length of SL-225 was significantly stimulated, when compared with that of Koshihikari. This result suggests that this QTL could play an important role in nitrogen utilization under the limited supply of NH₄⁺. Backcrossed progenies, BC₁F₃ derived SL-225, was used for the high resolution mapping. The target QTL was narrowed down to approximately 150 kb-region on chromosome 8.