Essential traits for reproductive drought and heat stress tolerance of Sabour Ardhjal rice: Implication for agricultural improvement

Sabour Ardhjal is a rice variety which demonstrates promising morphological and physiological characteristics associated with drought tolerance, while maintaining a relatively high grain yield. The present study is based on four years of experiment to bring forth the basic morpho-physiological and biochemical responsive patterns of rice variety Sabour Ardhjal, to assess its essential traits when exposed to individual drought, heat and in combination of drought and heat together. Results revealed significant alterations amongst the stresses applied; in plant architecture, with the most pronounced reductions in panicle and flag leaf length occurring under combined stress. Floral traits were also impacted, with delayed flowering times under drought and combined stress. Physiological responses to stress included increased canopy temperature and reduced relative water content. Chlorophyll content decreased significantly under combined stress, while photosynthesis rates were reduced across all treatments. Stomatal conductance showed minimal variation, suggesting that stomatal regulation was not the primary factor limiting photosynthesis. Biochemical analyses revealed increased lipid peroxidation and electrolyte leakage, indicating membrane damage during the heat stress and combined stress. Reactive oxygen species (ROS) generation was elevated under all stress conditions, with the highest levels observed under combined stress. Antioxidant enzyme activities increased to mitigate oxidative stress, while proline accumulation served as an osmolyte to maintain cellular turgor. Correlation analyses identified significant relationships between morphological, physiological, and biochemical traits with grain yield. These findings highlight the complex interplay of factors influencing rice performance under stress conditions and provide insights for important traits for breeding programme aim at developing multiple stress-tolerant varieties.