Cold stress in apple: the antioxidant defense mechanisms for the prediction of sunscald disorder during postharvest storage
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Abstract
Abiotic stresses, including low temperatures, severely af- fect yield and productivity of plants worldwide. Detection and signalling of low temperature is a complex process and dramatically alters the physiological, biochemical and morphological processes of plants. In addition of these effects in plants, cold stress promotes the development of a physiological disorder in fruits: sunscald. It af- fects the postharvest quality of apple (Malus domestica Borkh) leading to important economic losses worldwide. In this study, Granny Smith apple was harvested from ho- mogenous trees. Five replicates of 100 apples per replicate per sunburn category were stored at 0-2 °C. Fruit clas- sification was done according the following categories: ‘Exposed’ (Exp), ‘Moderate’ (Mod) and ‘Severe’ (Sev). As results, significant decrease in protein, SOD, MDHR and GR activities were signaled in the case of the severity category (Sev.) compared to the others of sunburn category (Mod and Exp). The activity of DHAR was the same in all the categories (Exp, Mod and Sev.) of the fruit during the storage period. As a conclusion, all the fruits related to the suburn category have almost no antioxidant metab- olism and antioxidant enzymes to deal with post-harvest oxidative stress. These antioxidant systems have already been overwhelmed due to photo-oxidative stress in the field.
