Heat Stress Tolerance in Rice (Oryza sativa L.): Identification of Quantitative Trait Loci for Seedling Growth Under Heat Stress.

Productivity of rice, world’s most important cereal is threatened by high temperature stress, intensified by climate change. Development of heat stress-tolerant varieties is one of the best strategies to maintain its productivity. However, heat stress tolerance is a multigenic trait and the candidate genes are poorly known. Therefore, we aimed to identify quantitative trait loci (QTLs) for vegetative stage tolerance to heat stress in rice and prioritize candidate genes using RNA sequencing. We used genotyping-by-sequencing to generate single nucleotide polymorphic (SNP) markers for 150 F₈ recombinant inbred lines obtained by crossing heat tolerant ‘N22’ and heat susceptible ‘IR64’ varieties. A linkage map was constructed using 689 recombinationally unique SNP markers in this mapping population. Heat stress tolerance was assessed by measuring shoot and root length of germinating seedlings under dark, incubated at control (28°C) and heat stress (37°C) conditions. Mapping analysis revealed a total of 15 QTL, out of which two were responsible for both root and shoot stress tolerance. These QTL contributed between 5.3 and 20.4% effect on the parameters measured. We used RNA Sequencing analysis of ‘N22’ and ‘IR64’ roots under control and stress conditions to identify potential candidate genes for heat stress tolerance.