Evaluation of Basmati Rice (Oryza sativa L.) Genotypes for Seedling Growth and Leaf Physiology Under High-Temperature Stress

Rice, a staple food crop for over half of the global population, is facing a serious threat of rising temperature due to climate change, especially in the areas producing Basmati rice. The main objectives of the study were to compare the promising cultivars of Basmati rice for heat stress tolerance and to assess how elevated temperature affects leaf physiological and morphological parameters of fine rice at seedling stage. A 2-year-controlled pot experiment was carried out to evaluate how different Basmati rice varieties respond to heat stress. The experiment was carried out at the Agronomic research area, University of Agriculture Faisalabad, Pakistan, during 2022 and 2023. The design of experiment was completely randomised design (CRD) with split treatment structure and four replications. Plant morphology, leaf temperature, chlorophyll contents, relative cell injury and relative water contents were evaluated for both experimental years. Heat stress significantly affected all morphological and physiological attributes such as chlorophyll contents, relative water contents and relative cell injury across different varieties. There was variation in the behaviour of different varieties under stress conditions as compared to no heat, but from the results it was very clear that Kisan Basmati and PK-1121 Aromatic constantly showed poor performance under both conditions for all the recorded parameters. However, in almost each parameter evaluated, Basmati-515, Super Basmati and NIAB-16 exhibited Superior thermo tolerance and better performance. On the basis of observed morphological and physiological attributes, Kisan and PK-1121 Aromatic Basmati were graded as sensitive varieties, while Basmati-515, Super Basmati and NIAB-16 showed tolerance to heat stress as compared to other varieties. However, further research is needed to explore the underlying mechanisms and genetic factors contributing to the sensitivity or tolerance observed in these varieties.