Heat stress responses in common bean genotypes

This study investigated the physiological and molecular responses of two common bean ( Phaseolus vulgari s L.) genotypes, “Balkız” and “Local Genotype”, which differ in their relative heat tolerance, with the “Local Genotype” being more tolerant than “Balkız”, to high-temperature stress during the seedling stage, aiming to identify genotype-specific physiological and biochemical responses and to determine reliable indicators of thermotolerance. Leaf relative water content (RWC), turgor loss, membrane damage, proline levels, total soluble protein (TSP), and the expression of heat shock proteins HSP23 and HSP60 were examined. The “Local Genotype” exhibited greater thermotolerance, with lower membrane damage while the temperature at which 50% injury occurs (LT50) was higher, despite the accumulation of less proline than “Balkız”. Genotype-specific variations detected in protein expression indicate distinct biochemical responses to heat stress. HSP23 showed a rapid, transient increase at moderate temperature (40 °C) in both genotypes, suggesting it has a role in early heat stress response. HSP60 levels were maintained near LT50 temperatures, supporting sustained stress adaptation, but declined at 48 °C, reflecting extreme stress rather than genotype-specific differences. These findings emphasize LT50 and HSP dynamics as key indicators of thermotolerance and provide insights for understanding heat stress responses in common bean seedlings.