Study On The Influences Of Different Bagging Dates On Apple Fruit Qualities Of 'Danxia'

Fruit bagging can greatly improve the interior and exterior qualities of apple fruit.However,fruit qualities may be greatly affected if bagging is carried out too early or too late.Therefore,appropriate bagging time selection has great importance to improve the quality of apple fruits.'Danxia' apple trees were used as the experimental material in this study and bagging treatments were conducted from 30 to 60 days after full bloom with five days' intervals.The local fruit bagging time was used as control.The exterior qualities and interior qualities of the fruits under different bagging date treatments were measured and evaluated at fruit mature period.The results are as follows:1.Influence of different bagging dates on 'Danxia' apple's exterior qualities:'Danxia' apple's fruit weight was increased gradually as the bagging time delaying.Bagging at 60 d after full bloom resulted in the highest fruit weight(208 g),which was significantly higher than other treatments.Fruit shape index of 'Danxia' apple were from 0.912 to 0.932 under different bagging dates whcih increased gradually along with the bagging time delayed.However,there were no significant differences among treatments.The sunscald index and black spot index of 'Danxia' apple fruit decreased as the bagging time delayed and bagging at 60 d after full bloom resulted in the lowest fruit sunscald index and the black spot index(0.3 and 0.4 respectively);The surface roughness index and fruit russeting index of 'Danxia' apple fruit increased as the bagging time delayed and bagging at 60 d after full bloom resulted in the the maximum values of the fruit roughness index and the fruit russeting index(0.8 and 0.6 respectively).The chlorophyll and carotenoid contents were all on the rise as the bagging time delayed and bagging at 60 d after full bloom resulted in the highest chlorophyll and carotenoid content(0.8 ?g·g-1 and 0.60 ?g·g-1 respectively)which were significantly higher than that of other treatments;The anthocyanin content in fruit skin increased gradually as the bagging time delayed,and it peaked when fruits were bagged at 50 d after full bloom(0.70 mg·g-1),then fell slightly and peaked again at bagging date of 60 d after full bloom.2.Influence of different bagging dates on 'Danxia' apple's exterior internal qualities:Bagging time has little effect on fruit hardness of 'Danxia' apple' and there were no obvious patterns of fruit hardness as the bagging time delayed while fruit soluble solids contents of danxia apple increased gradually.The fruit soluble solids content reached to its highest(17.7%),under bagging treatment 50 d after full bloom and it was significantly higher than other treatments;The fruit titratable acid contents,on the other hand,decreased along with the bagging time delayed and bagging at 60 d after full bloom resulted in the lowest(0.358%)which was significantly lower than other treatments..To sum up,the interior and exterior qualities of 'Danxia' apple fruit effected by bagging dates reached to a balanced state between 50 d to 60 d after full bloom.During this bagging period,fruit was larger,fruit surface smoothness was higher,anthocyanin content and ratio of fruit soluble solids and titratable acid were both higher,and the flavor was better.Therefore,bagging at 50-60 d in Jinzhong area After full bloom resulted in the best fruit qualities which suggested that 50-60d after full bloom was the best bagging time for 'Danxia' apple.