‘Saebonghwang’ was developed as a mid-late ripening rice variety with good cultivation stability and yield in transplanting and under direct seeding cultivation. It was bred by backcrossing ‘Hopum’, which has excellent cultivation stability and adaptability to direct seeding, as a repeat parent, and ‘Hitomebore,’ a Japanese rice variety with excellent taste, as a donor. The heading date of ‘Saebonghwang’ was August 11 under ordinary planting, which is two days earlier than that of ‘Nampyeong’, and August 13 under wet-direct seeding cultivation, which is the same as that of ‘Dongan’. ‘Saebonghwang’ had a culm length of 74 cm under wet-direct seeding cultivation, which is larger than that of ‘Dongan’ (69 cm), and had good cultivation stability, including lodging resistance. ‘Saebonghwang’ is resistant to bacterial leaf blight and rice stripe virus and shows moderate resistance to rice blast. Furthermore, ‘Saebonghwang’ has better grain appearance, superior taste and better milling characteristics than ‘Nampyeong’. The yield of ‘Saebonghwang’ when cultivated under ordinary planting, wet-direct seeding, and double cropping was 5.65, 5.37, and 5.37 MT/ha, respectively. Under wet direct sowing by drone cultivation, ‘Saebonghwang’ showed good initial survival rate and cultivation stability. The yield was 4.49 MT/ha, slightly lower than that obtained under transplanted cultivation (5.03 MT/ha), but was not statistically different; therefore, ‘Saebonghwang’ was adjudged to be adaptable to drone wet-direct seeding. ‘Saebonghwang’ can be used in various ways to suit the working conditions of farms, increase farm work efficiency, and expand the area of wet direct-seeding cultivation (Registration No. 9171).

Hypoxia caused by water seeding of rice inhibits germination and often leads to serious problems in seedling establishment and early growth. To solve this problem, it is necessary to develop rice cultivars that can stably germinate and grow under anaerobic environments. In this study, we performed QTL analysis on anaerobic germination (AG) tolerance using 139 recombinant inbred lines (RILs) derived from a cross between Milyang23 and Gihobyeo, and identified two QTLs (qAG2.1, qAG2.2) on chromosome 2. The LOD scores at qAG2.1 and qAG2.2 were 3.30 and 5.31, respectively. The phenotypic variances explained by the QTLs were 9.19% and 14.99%, respectively. The japonica cultivar Gihobyeo provided alleles for AG tolerance at both QTLs. While the chromosomal location of qAG2.2 overlapped with previously identified QTLs for AG tolerance, qAG2.1 was detected in a locus that has not been reported previously. The RILs carrying favorable type alleles for the AG tolerance at both QTLs (qAG2.1 + qAG2.2) expressed 41.0% survival rate under the AG condition, which was significantly higher than those of the RILs carrying single QTL, qAG2.1 (22.0%) or qAG2.2 (26.2%). As the favorable alleles for the two QTLs found in this study derived from the japonica cultivar Gihobyeo, it is expected that they would accompany less linkage drag such as shattering and lodging compared to those derived from indica or landraces. The result of this study would provide useful information for improving AG tolerance of japonica rice cultivars that can be used for water seeding cultivation.