Rice production is largely affected by various environmental conditions such as cold, heat and flooding. Here, to identify cold tolerant QTLs at seedling stage in rice, we generated RIL population derived from a cross between Hanareum 2 and Unkwang which are a highly cold sensitive and cold tolerant, respectively. We observed cold phenotype of this population in the growth chamber conditions and natural field conditions. For observation of cold tolerant phenotype of RIL population in the growth chamber, we treated cold stress (5~13°C) for 14 days and recovery for 4 days. When we examined the phenotype of RIL in the field conditions, temperature range in the field conditions was about 6 to 25°C in 2015~2016. We named QTLs as Seedling Cold Tolerant (SCT) in growth chamber and Cold induced Yellowing Tolerant (CYT) in the field, respectively. Three QTLs for SCT and 5 QTLs for CYT were detected on chromosome 1, 6, 7, 8, 10, 11 and 12. Among these QTLs, qSCT12 on chromosome 12 showed 26.3 LOD score with 25.5% of phenotypic variation. When qSCT11.1 and qSCT12 were combined, cold tolerant was most strongest in our experimental conditions. qCYT10 on chromosome 10 was identified in field experiment on both 2015 and 2016. These results may provide useful information for a marker-assisted breeding program to improve cold tolerance in rice.

The 'Misomi' is a rice variety derived from a cross between ‘Sobi’ which has adaptability of low fertilizer cultivation and SR21110 (Ilpum/Jinbu19) by the rice breeding team at National Institute of Crop Science, RDA in 2013. The heading date of ‘Misomi’ is August 14 and six days later than check variety, ‘Hwaseong’. It has 83 cm of culm length and 121 spikelets per panicle. It showed weaker cold tolerance than that of ‘Hwaseong’ during exposed to cold stress. ‘Misomi’ showed resistance to blast disease, K1, K2 and K3 race of bacterial blight and stripe virus, but susceptibility to K3a race, other viruses and planthoppers. The milled rice of this variety exhibits translucent, clear non-glutinous endosperm and short grain shape. It has low protein content (6.2%) and similar amylose content (19.4%) to that of ‘Hwaseong’. ‘Misomi’ showed better palatability index of cooked rice than that of ‘Hwaseong’. Particulary, ‘Misomi’ showed excellent processing adaptability than ‘Chucheong’ and ‘Hwaseong’ on palatability index of cold and aseptic cooked rice. Its milled rice recovery rate is similar to those of ‘Hwaseong’. However, whole grain rate of milled rice is higher than that of ‘Hwaseong’. 'Misomi' has 5.68 MT/ha of milled rice productivity in ordinary cultivation, which was 12% higher than that of ‘Hwaseong’. 'Misomi' could be adaptable to the middle plain area and Midwest coast area in Korea (Grant No. 5635).

The ‘Jungmo1023’ is the japonica rice variety developed from a cross between Yeongdeog34 and F1 of Iksan456 and SR21097-B-B-19-2-2 by the rice breeding team at NICS in 2012. The heading date of ‘Jungmo1023’ is August 3 in middle plain area and it is six days earlier than ‘Hwaseong’. ‘Jungmo1023’ has 80 cm of culm length which is 4 cm shorter than those of ‘Hwaseong’ and 107 spikelet per panicle. The premature heading rate of ‘Jungmo1023’ was 3.3%. It showed resistance to blast, bacterial blight (K1, K2, K3 race) and stripe virus, but susceptibility to K3a race of bacterial blight, dwarf and black streak dwarf viruses and planthoppers. The milled rice of this variety exhibits translucent and medium short grain shape. It has better palatability index of cooked rice (0.24) and lower amylose content (18.0%) than that of ‘Hwaseong’. The characteristics related to grain milling were better than those of ‘Hwaseong’, especially head rice milling recovery ratio and head rice ratio (96.2%). ‘Jungmo1023’ showed 4.56 MT/ha of milled rice productivity at 7 sites in ordinary cultivation. However, ‘Jungmo1023’ showed early cultivation culture adaptability because of 98% of its yield potential (4.99 MT/ha) compared to high yielding early-maturing variety ‘Jopyeong’. ‘Jungmo1023’ could be adaptable to the middle plain, mid-mountainous and north-east coastal area in Korea (Registration No. 5115).