Change of Organic Acid Contents and Related Enzyme Activities in Different Pear Cultivars

In this study,the pear cultivar‘Yali',‘Chili'and‘Balixiang'were used to determine the dynamic change of fruit organic acids accumuation and related enzyme activities during fruit development,the correlation of organic acids contents and the activities of related enzyme were also explored.The results demonstrated that:(1)The contents of organic acids decreased gradually during fruit development.The total organic acid content of‘Chili'was the highest,followed by‘Yali',and the‘Balixiang'is the least at the period of fruit ripening.Furthermore,the total organic acid content showed significant difference among three cultivars.(2)At the later stage of fruit development,the content of citric acid of‘Yali',‘Chili'and‘Balixiang'was almost the same,but the content of malic acid showed significant difference among three cultivars,which indicated that malic acid played an important role in the difference of organic acid content of different cultivars.(3)NADP-ME activity showed significant difference during late stage of fruit development,however,NAD-MDH and PEPC activities showed no significant difference in synthesis of malic acid,so the NADP-ME was an important enzyme involved in the difference of malic acid content among‘Yali',‘Chili'and‘Balixiang'.(4)The related enzymes of CS,Cyt-ACO,Mit-ACO and NAD-IDH in synthesis pathway of citric acid showed same trends in different cultivars,but no significant difference at late stage of fruit development,which suggested that they were not main factors leading to the difference of citric acid content.(5)The correlation analysis between organic acid content and activities of related enzymes during the fruit devlopment revealed that both of enzyme activities in malic acid and citric acid synthesis pathway affected the total level of the organic acid content together.