Physiological and Biochemical Indicators of Cold Acclimation in Five Iranian Pomegranate (Punica granatum L.) Cultivars: Insights from Leaf and Shoot Bark Responses

The correlation between physiological and biochemical indices of leaves and shoot bark with the acclimation of pomegranate cultivars to freezing stress is crucial for better orchard management and pomegranate breeding. The objectives of our study were to identify physiological and biochemical indicators related to freezing stress for the selection of resistant cultivars. To this end, five commercial pomegranate cultivars were studied under freezing stress, and the correlation between electrolyte leakage (EL) and biochemical and physiological traits of shoot bark and leaves was calculated. This study was conducted as a factorial experiment in a completely randomized design with six replications. The factors included cultivar at five levels (‘Gorj-e-Shahvar’ (GS), ‘Post Ghermaz-e-Aliaghai’ (PGA), ‘Khafr-e-Jahroom’, ‘Zagh-Yazdi’ (ZY), and ‘Rabab-e-Neyriz’), temperature at five levels (−2°C, −6°C, −10°C, −14°C, and −18°C), and duration of freezing treatment at two levels (one and 2 h). Our results indicated that the resistance mechanisms of cultivars differed depending on the temperature and treatment duration. GS exhibited the lowest percentage of EL and the highest LT50, while the ZY and PGA cultivars showed the highest percentage of EL and the lowest LT50.