Quantitative Trait Locus (QTL) and Candidate Gene Analysis of Heat Tolerance During the Rice Seedling Stage

Rice (Oryza sativa L.) is a major staple crop in China, but high-temperature heat stress has become one of the key factors threatening national food security, causing symptoms such as leaf curling, chlorosis, and water loss-induced wilting. In this study, we used indica rice ‘HZ’ (Oryza sativa L. subsp. indica cv. ’HZ’), japonica rice ‘Nekken2’ (Oryza sativa L. subsp. japonica cv. ’Nekken2’), and their derived 120 recombinant inbred lines (RILs) as experimental materials. Phenotypic data including seedling survival rate, heat tolerance rating, and seedling growth rate were measured, and quantitative trait locis (QTLs) associated with rice seedling heat tolerance were mapped using a high-density genetic map. A total of 31 QTLs related to heat tolerance were detected, with logarithm of odds (LOD) values ranging from 2.06 to 5.09. Additionally, 12 candidate genes were identified within these QTL intervals. Real-time quantitative reverse transcription PCR (qRT-PCR) analysis revealed that LOC_Os03g45330, LOC_Os04g32560, and LOC_Os10g26720 associated with rice heat tolerance, whereas LOC_Os01g46080 and LOC_Os07g08340 may contribute to it. These findings provide important insights for further elucidating the molecular mechanisms underlying heat stress response in rice and for breeding new high-quality heat-tolerant rice varieties.