Effects of different pollination combinations on ASA content, activity of antioxidant coordinating enzymes and dynamic changes of sugars and organic acid compositions in apple fruits

Abstract:【Objective】The metabolism of sugars and acids affects fruit development, antioxidation and dynamic changes of sugar/organic acid compositions in apple fruits. The antioxidant activity in the fruits is an important character for apple quality. This paper dealt with the differences of ASA (ascorbic acid, ASA) contents, sugars/organic acids composition and the activity of antioxidant coordinating enzymes in apple fruits during growth and development in relation to different pollinatiom combinations.【Methods】The flowers of‘Fuji' (Malus domestica Borkh.) and‘Gala' (Malus domestica Borkh.) were pollinated in belly stage of blooming by pollens collected from the pollination trees Malus spp. (1379, 1539, 1-17, 3-21) , and‘Starkrimson' (Malus domestica Borkh.) as contrast. The fruit composition of acids including oxalic acid, tartaric acid, malic acid, lactic acid, acetic acid, succinate, citric acid, the composition of sugar including glucose, fructose, sucrose and sorbitol, and antioxidant enzymes including superoxide dismutase (SOD) , peroxidase (POD) , catalase (CAT) activity and malondialdehyde (MDA) content were determined during the fruit development every 20 days. The sugars and the organic acid were separated and quantified by HPLC analysis. The HPLC system contained a quaternary pump, an autosampler, and a reflective index detector (Waters 410) with Hyper REZ XP Carbohydrate Ca2+8 ìm column at 80 ℃ with a flow rate0.5 m L·min^-1. The mobile phase was performed with an isocratic elution of ultrapure water for peak separation. At last, the data were presented as the mean ± standard deviation of triplicate.【Results】Different pollens had different effects on the contents of the ASA in the fruits, and the contents of ASA increased significantly during 40-60 days after pollination. The content of the ASA in the fruits pollinated by the 4tested pollinators was higher than that of the control obviously. The activity of superoxide dismutase (SOD) , and peroxidase (POD) had the same changes as the ASA, that is, they decreased firstly, then increased, and decreased again at last. The catalase (CAT) activity decreased gradually while the content of malondialdehyde (MDA) increased at first, and then decreased. Activities of antioxidant isozymes in the fruits pollinated by the 4 tested pollination trees were higher than those of the control. In the late stage of the fruit growth, contents of total acids, the malic acid, citric acid and succinate in the fruits pollinated by the 4 tested pollination trees were lower than those of the control, while the contents of oxalic acid and tartaric acid in the fruits pollinated by the 4 tested pollination trees were higher than those of the control.The sugar content in the fruits pollinated the 4 tested pollinators was higher than that of the control, and the contents of fructose and sucrose in the fruits pollinated by the 4 tested pollination trees were significantly higher than those of the control. The contents of tartaric acid and oxalic acid in the fruits pollinated by the 4 tested pollination trees were higher than those of the control, but the total content of the acid in the fruits pollinated by the 4 tested pollination trees was lower than that of the control. Meanwhile, the contents of the fructose and sucrose in the fruit pollinated by the 4 tested pollination trees were significantly higher than those of the control, but the differences of sugar and organic acid compositions in the fruits pollinated by different pollen donors were not statistcally obvious.【Conclusion】The main soluble sugars in the fruits of the apple cultivars tested were glucose and fructose, the main organic acid was malic acid. The contents of the ASA in apple fruits could be significantly increased by using more suitable pollination trees, but the difference of the contents of the ASA in the fruits derived from the pollinating trees except for the control were not statistically significant. The contents of tartaric acid and oxalic acid in the fruits pollinated by the 4 tested pollination trees were higher than those of the control, but the total content of the acids in the fruits pollinated by the 4 tested pollination trees was lower than that of the control. Meanwhile, the contents of the fructose and sucrose in the fruits were significantly increased by using the pollinating trees except for the control. The change of the antioxidant activity was similar to the content of ASA, and it seems to be possible that that the antioxidant activity and the ASA content was related to each other.