Abstract
In cereals, root elongation is stimulated under low nitrogen concentration. Toward isolation of regulatory genes for NH4+ use efficiency, chromosome segment substitution lines developed between Koshihikari and Kasalath were employed to detect QTLs of root elongation under various concentrations of NH4+. Germinated seedlings were hydroponically grown with 5, 50 or 500 μM NH4+ for 7 days, and then maximum length of roots were determined. In particular, Kasalath allele on QTL in long-arm of chromosome 6 greatly promoted the root elongation under all concentrations. This allele increased nitrogen content of whole plants when grown with 50 or 500 μM NH4+ not but with 5 or 1000 μM. These results suggest that the QTL gene could play an important role in controlling of NH4+ use efficiency at a specific range of NH4+ concentration. High-resolution mapping revealed that the target QTL was delimited in a 24.3 kb region.
