QTL mapping for seedling traits associated with low-nitrogen tolerance using a set of advanced backcross introgression lines of rice.

Nitrogen (N) deficiency is a major yield-limiting factor in rice production. The objective of this study was to identify putative QTLs for low-N stress tolerance of rice, using an advanced backcross population derived from crosses between an indica cultivar '93-11' and a japonica cultivar 'Nipponbare' and genotyped at 250 marker loci. Plant height, maximum root length, root dry weight, shoot dry weight and plant dry weight under two N conditions and their relative traits were used to evaluate low-N tolerance at the seedling stage. A total of 44 QTLs were identified on chromosomes 1, 2, 3, 4, 5, 6, 8 and 9. Eight intervals on five chromosomes were identified to harbour multiple QTLs, suggesting pleiotropism or multigenic effects according to the contributor of alleles. Some QTL clusters were found in the nearby regions of genes associated with N recycling in rice, indicating that the key N metabolism genes might have effects on the expression of QTLs. Several unique QTLs for relative traits were detected, which suggested the specific genetic basis of relative performance. [ABSTRACT FROM AUTHOR]