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

Abstract

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_2:3 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, <i>qHTT8</i>, controlling HT was identified on chromosome 8 using the bulked-segregant analysis (BSA)-seq method. The QTL <i>qHTT8</i> was mapped into the 3,555,000-4,520,000 bp, which had a size of 0.965 Mb. The candidate region of <i>qHTT8</i> 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. <i>LOC_Os08g07010</i> and <i>LOC_Os08g07440</i> were highly induced in HHZ compared with 9311 under heat stress. Orthologous genes of <i>LOC_Os08g07010</i> and <i>LOC_Os08g07440</i> in plants played a role in abiotic stress, suggesting that they may be the candidate genes of <i>qHTT8</i>. Generally, the results of this study will prove useful for future efforts to clone <i>qHTT8</i> and breed heat-tolerant varieties of rice using marker-assisted selection.