Brassinosteroid Enhances Cold Stress Tolerance of Washington Navel Orange (Citrus sinensis L.) Fruit by Regulating Antioxidant Enzymes During Storage

The effect of brassinosteroid (BR) on chilling injury of Washington Navel orange (Citrus sinensis L.) fruit was investigated. BR at the concentrations of 0.75 and 1.5 ppm effectively reduced chilling injury of Washington Navel orange fruit during five months storage at 3°C, and BR at 1.5 ppm showed the best effect. BR treatment also reduced the lipid peroxidaion and peroxide hydrogen content of peel and pulp during storage. Results of physiological response in orange fruit showed that BR induced the activity of antioxidant enzymes including catalase and peroxidase. These results indicate that the elicitation of an antioxidant response in orange fruit by BR may be associated with chilling injury alleviation. Moreover, BR maintained the orange quality by decrease of lipid peroxidation and peroxide hydrogen content. The present study is the first evidence that BR enhances orange fruit tolerance to cold stress and therefore fruit quality