Heterosis describes the increased performance of F1 hybrid plants in terms of increased biomass, yield, vegetative growth rate, and tolerance against biotic and abiotic stresses as compared with their inbred parents. Two sets of rice materials, 166 RILs derived from a cross between Milyang 23 (Korean indica-type rice) and Tong 88-7 (japonica Rice), and BC1F1 hybrids derived from crosses between the RILs and the female parent, Milyang 23, were produced to identify QTLs for heterosis of yield and yield-related traits. The QTLs were detected from three different phenotype data sets including the RILs, BC1F1 hybrids, and mid-parental heterosis data set. A total of 57 QTLs were identified for nine traits. Of eight QTLs detected for yield heterosis, five overlapped with other heterosis QTLs for yield-related traits such as spikelet number per panicle, days to heading, and spikelet fertility. Four QTLs for yield heterosis, gy1.1, py6, gy10, and py11, were newly identified in this study. We identified a total of 17 EpQTLs for yield heterosis that explain 21.4 ~ 59.0 % of total phenotypic variation, indicating that epistatic interactions may play an important role in heterosis.

• Sang-Ho Chu(Department of Plant Science, Plant Genomics and Breeding Institute, Research Institute for Agriculture and Life Sciences, Seoul National University)
• Wenzhu Jiang(Department of Plant Science, Plant Genomics and Breeding Institute, Research Institute for Agriculture and Life Sciences, Seoul National University)
• Joong-Hyoun Chin(Plant Breeding, Genetics and Biotechnology, IRRI, Philippines)
• Hee-Jong Koh(Department of Plant Science, Plant Genomics and Breeding Institute, Research Institute for Agriculture and Life Sciences, Seoul National University) Corresponding Author