This study was conducted to identify QTLs for some agronomic traits under two different N-fertilizer conditions. A recombinant inbred population (DT-RILs) between Dasanbyeo (a tongil type rice, derived from an indica × japonica cross and similar to indica in its genetic make-up) and TR22183 (a Chinese japonica variety), consisting of 166 F8 lines, was developed and used for mapping. A frame map of 1,409 cM containing 113 SSR and 103 STS markers with an average interval of 6.5 cM between adjacent marker loci was constructed using the DT-RILs. The DT-RILs were cultivated in ordinary N-fertilizer (N-P2O5-K2O=100-80-80 kg/ha) condition and low N-fertilizer (N-P2O5-K2O=50-80-80 kg/ha) condition in order to compare the different N-fertilizer effects. Grain yield was positively correlated with spikelet number in both conditions. Path analysis revealed that spikelet number is the most positive contributor to grain yield. Twenty-nine single QTLs (S-QTLs) and sixty-five pairs of epistatic loci (E-QTLs) were identified for days to heading, culm length, panicle length, panicle number, spikelet number, spikelet fertility, 1000-grains weight and grain yield in both N-fertilizer conditions. The phenotypic variance explained by these S-QTLs and E-QTLs ranged from 8.8% to 61.1% and from 10.0% to 55.6%, respectively. The total phenotypic variance explained by all the QTLs for each trait ranged from 15.4% to 92.3%.

• Young Il Cho
• Hee Jong Koh