Identification and Fine Mapping of a Major QTL, TT1-2 , That Plays Significant Roles in Regulating Heat Tolerance in Rice

Global warming threatens many aspects of human life, including a reduction in crop yields, and breeding heat-tolerant crops is a fundamental way to help address this challenge. As food for more than half of the global population, rice ( Oryza sativa ) has always been a popular research material in plant science. Breeding heat-tolerant rice using genes affording thermotolerance is a fundamental way to address this challenge. In this study, a major QTL, TT1-2 , was found to regulate heat tolerance in rice; this QTL was controlled by a single dominant gene. Using F 2:3 populations, we narrowed TT1-2 to a 26.0-kb region containing three putative genes, one of which encodes an α2 subunit of the 26S proteasome. This gene was considered the TT1-2 candidate, and the TT1 gene involved in rice heat tolerance was present at this locus. Further analysis showed that the amino acid sequence of the TT1-2 gene had one amino acid difference: arginine (R)-99 was changed to histidine (H), which leads to the formation of a normal alpha-helix. Moreover, through marker-assisted selection and conserved breeding selection, we developed a new male-sterile line, Zhehang 10A, which had a high outcrossing rate, good quality, and strong heat tolerance. We then used Zhehang 10A as the female parent and the restorer line Fuhui 1586 as the male parent and bred a new hybrid, Zhehangyou 1586, which showed high yield, good quality, and strong heat tolerance.