QTL Mapping and Identification of Candidate Genes for Heat Tolerance at the Flowering Stage in Rice.

High-temperature stress can cause serious abiotic damage that limits the yield and quality of rice. Heat tolerance (HT) during the flowering stage of rice is a key trait that can guarantee a high and stable yield under heat stress. HT is a complex trait that is regulated by multiple quantitative trait loci (QTLs); however, few underlying genes have been fine mapped and cloned. In this study, the F population derived from a cross between Huanghuazhan (HHZ), a heat-tolerant cultivar, and 9311, a heat-sensitive variety, was used to map HT QTLs during the flowering stage in rice. A new major QTL, , controlling HT was identified on chromosome 8 using the bulked-segregant analysis (BSA)-seq method. The QTL was mapped into the 3,555,000-4,520,000 bp, which had a size of 0.965 Mb. The candidate region of on chromosome 8 contained 65 predicted genes, and 10 putative predicted genes were found to be associated with abiotic stress tolerance. Furthermore, qRT-PCR was performed to analyze the differential expression of these 10 genes between HHZ and 9311 under high temperature conditions. and were highly induced in HHZ compared with 9311 under heat stress. Orthologous genes of and in plants played a role in abiotic stress, suggesting that they may be the candidate genes of . Generally, the results of this study will prove useful for future efforts to clone and breed heat-tolerant varieties of rice using marker-assisted selection.