Fruit Sugar and Acid Content, Variation at Different Fruit Development Stages and Their Relationship with Leaf Soluble Sugar Content of Blueberry

【Objective】An experiment was conducted to study the characters of sugar and acid content and analyze the relationships of sugar content in fruits and leaves during fruit development, thus providing a theoretical basis for metabolic mechanism of sugar and acid and quality regulation, in blueberry.【Method】Five cultivars of three taxonomic types, including high bush blueberry, e.g. ‘Spartan' and ‘Jersey', half-high bush blueberry, e.g. ‘North country' and ‘North blue' and low bush blueberry,e.g. ‘Blomidon' were used to investigate the seasonal variation of sugar and acid content in fruits and leaves at different fruit development stages by high performance liquid chromatography(HPLC). 【Result】The results indicated that the average content of total sugar was 102.04 mg·g-1FW, the highest and lowest of total sugar content existed in ‘Spartan' and ‘North country', respectively.Glucose and fructose content increased during fruit maturation and the contents of them accounted for 97.90%-99.47% of total sugar content in mature fruit, the ratio of them was 1:1, whereas the sucrose and sorbitol contents decreased constantly from a low level during fruit maturation into traces of them in matured fruit. The average content of total acid was 7.10 mg·g-1FW, in tested high bush blueberry and half-high bush, citric acid was the major organic acid, accounted for 76.94% of total acid in mature fruit which increased at early stage, and decreased quickly till fruit maturity, quinic acid and malic acid contents decreased gradually. There was a similar change trend and component in both low bush cultivars ‘Blomidon' and half-high bush cultivar ‘North country', with quinic acid being the main acid and it presented a decline tendency during the fruit development stage, the content was higher than other cultivars in matured fruit, citric acid and tartaric were the minor components; Sorbitol accounted for 67.28% of total sugar in leaves,and the content reached top at 42 d after full bloom(around 15 d before harvest), then decreased quickly.【Conclusion】The component characters of organic acid in ‘Blomidon' and ‘North country' were obviously distinguished from high bush and half-high bush blueberry. Sorbitol was the main soluble sugars in leaves. The stage of around 15 days before harvest was the critical period of fruit expansion growth and sugar accumulation.