Evaluation the Preharvest Application of Iron and Nitrogen on Some Qualitative Characteristics of Two Apple Cultivars during Cold Storage

Apple is one of the most important fruits in temperate zones with a long post-harvest life during cold storage. A factorial experiment, in a randomized completely block design was used to investigate the preharvest application of Iron (0, 500 and 1000 mg Fe-EDDHA per tree) and nitrogen (0, 48 and 96 g ammonium nitrate per tree( on some postharvest qualitative characteristics in "Red spur" and "Granny smith" apple cultivars. Iron and nitrogen treatments in all 72 trees were applied in three stages (full bloom, 30 and 60 days after full bloom). Fruit quality parameters including colorskin color parameters (L*, a*, b*), flesh firmness, total soluble solids (TSS), Titratable acidity (TA), flavor index (TSS/TA) and total antioxidant activity were measured. According to the results, a decrease in fruit firmness, TA and increase in TSS/TA in both cultivars were observed during cold storage irrespective of treatments. The results showed that in  “Red spur” cultivar, Fe application decreased fruit firmness, TSS, b* parameter values and increased TSS/TA, a* parameter values, while, N application increased TSS. Fruit firmness was decreased and TSS, TSS/TA, b* parameter values were increased by Fe application in  “Granny smith” cultivar. Fruit firmness, TSS and L* parameter values were decreased and TA was increased by N application on this cultivar. In conclusion, Fe and N application in proper levels improved some postharvest qualitative characteristics in "Red spur" and "Granny smith" apple cultivars during cold storage.