Effects of Elevated Temperature on Agronomic, Morphological, Physiological and Biochemical Characteristics of Potato Genotypes: 2. Physiological and Biochemical Traits

Heat stress represents a significant consequence of global climate dynamics, emerging as a primary focus in cultivar breeding objectives and sustainability efforts in many crops, including potato. This requires the need to evaluate the response of potato genotypes to heat stress under field conditions. This study evaluated potato genotypes’ physiological and biochemical responses to elevated temperatures. The experiments were conducted under field conditions in the 2022 and 2023 growing seasons in a split-plot design. Two temperature treatments were applied: a control treatment in which the plants received the field temperature of the experimental station and a heat treatment in which the plants received a temperature of + 6.0–10.0 °C depending on the time of the day. The results showed that elevated temperature significantly (P < 0.05) increased the leaf canopy temperature (CT), leaf area index (LAI), leaf chlorophyll content (SPAD), malondialdehyde (MDA), and proline while inducing a significant reduction in hydrogen peroxide (H₂O₂). The photosynthetic rate (Pn), stomatal conductance (Gs), and transpiration rate differed significantly (P < 0.001) between treatments in both seasons. Pn and Gs increased significantly with temperatures up to 37.0–39.0 °C, while further temperature increases resulted in heat shock and burning of potato leaves. Heat stress enhanced the activities of enzymes such as superoxide dismutase (SOD), catalase (CAT), and ascorbic peroxidase (APX) while decreasing the peroxidase (POD). The results suggest that heat-tolerant potato genotypes may possess an efficient defence mechanism against reactive oxygen species (ROS) by enhancing the antioxidant enzyme activity under heat stress and may be used as physiological and biochemical markers in screening heat-tolerance potato varieties.