Grain size is a major determinant of grain yield in rice. In a previous study, a QTL for grain width(GW), qgw1 was detected on chromosome 1 using 96 BC3F8 lines derived from a cross between ‘Hwaseongbyeo’ as a recurrent parent and ‘O. rufipogon’ as a donor parent. At this locus, the O. rufipogon allele increased GW. Among the 96 introgression lines, three ILs with the O. rufipogon qgw1 locus showed significantly increase in grain width compare to the recurrent parent. One of the three lines, CR572 was selected and crossed to ‘Hwaseongbyeo’. A total of 494 F2:3 were evaluated for grain width and agronomic traits in the field. QTL analysis in 494 F2:3 lines indicated that QTL for grain width was located in the interval RM495–RM5443. To narrow down the position of qgw1, substitution mapping using F4 lines with different cross-over breakpoints in the region is underway. The result will be discussed.

The objective of this study were to identify QTLs for agronomic traits using a set of introgression lines carrying wild rice (Oryza rufipogon) segment in cultivated rice (ssp. japonica cv. Hwaseongbyeo). Ninety-six ILs were evaluated for seven agronomic traits, amylose and protein contents. The proportion of the recurrent genome in ILs ranged from 87.8 to 100%, with an average of 96.7%. The mean number of homozygous and heterozygous donor segments were 2 (ranging 0-7) and 1.7 (ranging 0-6), respectively, and the majority of these segments had size less than 10 cM. A total of 22 quantitative trait loci were identified for 9 traits and each QTL explained 7.2% to 56.6% of the phenotypic variance. Some QTLs were clustered in a few chromosomal regions. A first cluster was located near RM527 on chromosome 6 with QTLs for culm length, panicle length, days to heading, 1000-grain weight and protein content. Three ILs with high spikelets per panicle compared to the recurrent parent were selected to detect and fine map the wild segments responsible for this variation. The results will be discussed.

In the previous study (Yuan et al. 2009), a quantitative trait locus (QTL) for grain weight was detected on the short arm of chromosome 5 using an advanced backcross lines (BC3F3) between Hwayeongbye (Oryza sativa) and W1944(Oryza rufipogon Griff.) .For detection of gw5 locus, a line CR6 (BC3F4) was selected and crossed to Hwayeongbyeo produce S1F2 and S1F3 population. And a plant from S1F3 population, carried W1944 homozygous segment for target region at gw5 was crossed to Hwayeong to produce S2F2 population. All these population including some S1F3 lines were grown in the field in 2007, 2008 and 2009, respectively (fig1). Frequency distribution of grain weight followed the Mendelian ratios(3:1) for single locus segregation (Χ2=1.22, 0.76, 1.34 in 2007, 2008 and 2009 respectively).In Hwayeongbye genetic background, the W1944 allele at the gw5 locusde creased grain weight, QTL analysis showed that gw5 co-segregated with RM18003 and RM194 (R2=62.7, 69.5 and 37.1% in 2007, 2008 and 2009 respectively). Addition, five QTLs plant height, culm length, secondary branch, spikelet number perplant and rationing ability were detected in the region around gw5, in 2008 and 2009. Substitution mapping with 32F3 lines, gw5 QTL was flanked by two SSRmarkers, RM18003 and RM194, in a300kb to 1.7Mb physical distance region,. QTL analysis indicated that 5 others QTLs plant height, culm length, secondary branch, spikelet number per plant and rationing ability were tightly linked.

A near-isogenic line CR1815, containing three introgressed segments on chromosomes 1, 7 and 9 from 0. rufipogon into the Oryza saliva cultivar Milyang23 background was developed based on MAS (marker aided selection) and backcrossing. The introgressed segm

Low temperature germination is one ofthe major determinants for stable stand establishment in the direct seeding method in temperate regions. Quantitative trait loci (QTLs) controlling low temperature germiability (LTG) and awn were confirmed in BC1F1 usi

This study was conducted to identify the genomic regions associated with cold tolerance in rice. An RIL population consisting of 120 lines was developed from a cross between the japonica cultivar, Hwayeongbyeo and the wild rice, Oryza rufipoon Griff. Acc.