Effect of Ca, Zn and B Spray Application on Preharvest Fruit Drop, Sugar and Nutrient Contents and on some Quantitative and Qualitative Fruit Characterestics in some Asian Pear (Pyrus serotina Rehd.) Cultivars

The effect of Ca، Zn and B spray application on preharvest fruit drop، sugars، calcium، zinc، and boron concentrations and as well on some physicochemical fruit properties of five commercial Asian pear cultivars (‘KS’7، ‘KS’8، ‘KS’11، ‘KS’12 and ‘KS’14) was investigated under Tehran Province،s environmental conditions. Trees were sprayed one month past fruit set until harvest within two week intervals with Ca، Zn، B and as well with their mixtures at 5% concentrations. Fruit drops were recorded from treatments، start untill harvest. At the time of fruit harvest، fruit sugar and mineral contents were determined using HPLC and ICP، respectively. Results revealed that Ca، Zn and B applications decreased preharvest fruit drop in a way that a combination of Ca، Zn، and B applications rendered a 6. 3% fruit drop in comparison with 17. 3% occurring in control. Throughout the research، fructose was found out as the dominant sugar followed by glucose، sorbitol and sucrose in the studied cultivars. Spray applications of Ca، Zn and B increased the fruits، fructose، glucose، sorbitol and sucrose contents in all the studied cultivars (1-2. 5، 1-2. 1، 2-3. 7 and 0. 7-2. 2 % fresh weight، respectively). In addition، total soluble solids increased by 1-2 ºBrix total sugars (1-2 % of fresh weight)، total acidity (0. 07-0. 12 mg 100-1g) and dry weight (1-1. 5g) of fruits in all cultivars. Spray of Ca increased fruit firmness (1-2 N varied with cultivar). Spray of Ca، Zn and B applications increased Ca، Zn and B mineral contents of both leaves and fruit.