Exploring Spikelet Fertility and HSP70 Expression as Indicators of High Temperature Tolerance in Rice

Abstract The expression patterns of potential biomarkers can aid in developing thermotolerant rice varieties, addressing food security challenges in times of climate change. This study validated the heat tolerance coefficient and spikelet fertility in rice by linking them to the expression pattern of HSP70. Relative membrane permeability (RMP), hydrogen peroxide (H₂O₂), and malondialdehyde (MDA) were measured alongside growth and yield data to assess cell membrane thermostability, oxidative stress levels, and lipid peroxidation. The differential expression of HSP70 was analyzed to identify biomarkers for thermotolerance. Significant varietal differences in thermotolerance were observed, with K-95 and IR-6 exhibiting robust HSP70 expression, early stress response, and minimal oxidative damage. In contrast, heat-sensitive varieties (DR-92 and DR-83) showed delayed HSP70 expression and poor physiological recovery. Early HSP70 induction under stress and sustained expression during recovery correlated with enhanced antioxidant defense and reduced stress-induced damage in thermotolerant cultivars