Mapping QTLs for nitrogen-deficiency tolerance at seedling stage in rice (Oryza sativa L.)

P>A recombinant inbred line (RIL) population, consisting of 238 F-12 lines derived from 'R9308'/'Xieqingzao B', the parents of a super hybrid rice in China, was developed for mapping quantitative trait locus (QTL) for nitrogen deficiency tolerance. A genetic linkage map with 198 simple sequence repeat (SSR) markers was constructed. Six traits of shoot dry weight (SW), root dry weight (RW), plant dry weight (PW), maximum root length (RL), chlorophyll content (Chl), plant height (PH) were used to assess the N-deficiency tolerance. The ratio of the parameters from the two treatments was calculated as derived parameters. QTL analysis detected seven QTLs on chromosomes 1, 2, 3 and 8 associated with N-deficiency tolerance in this mapping population. These QTLs explained 9.07-14.45% of the phenotypic variation. The 'R9308' alleles increased the relative traits except that of locus on chromosome 8. One of the major QTL clusters was detected in the interval RM5385-RM7192 on chromosome 1, which was associated with N recycling in rice. This chromosomal region may be enriched with the key N metabolism genes.