Quantitative trait loci associated with seed set under high temperature stress at the flowering stage in rice (Oryza sativa L.)

High temperature stress (HTS), an increasingly important problem in rice production, significantly reduces rice yield by reducing seed set percentage (SSP). Breeding rice varieties with tolerance to HTS at the flowering stage is therefore essential for maintaining rice production as the climate continues to warm. In this study, two quantitative trait loci (QTL) underlying tolerance to HTS were identified using the recombinant inbred lines (RILs) derived from a cross between the HTS-tolerant rice cultivar 996 and the sensitive cultivar 4628. SSP was used as the heat-tolerance indicator for the lines, which were subjected to HTS at the flowering stage in both field and growth chamber experiments. Two major QTL that affected SSP in both conditions were detected in the interval between RM5687 and RM471 on chromosome 4, and between RM6132 and RM6100 on chromosome 10. The QTL located on chromosome 4 explained 21.3% in field and 25.8% in growth chamber of the total phenotypic variation in SSP, and increased the SSP of plants subjected to HTS by 9.1% in field and by 9.3% in growth chamber. The second QTL located on chromosome 10 explained 11.5% in field and 11.6% in growth chamber of the total phenotypic variation in SSP, and increased the SSP of plants subjected to HTS by 7.2% in field and 7.0% in growth chamber. The positive additive effects of the two QTL were derived from the 996 alleles. The two major QTL identified in this study could be useful for further fine mapping and cloning of these genes and for molecular marker-aided breeding of heat-tolerant rice cultivars.