Effect of Bearing Shoot Leaves on the Sugar Content of Yunnan Early Maturing Citrus

Purpose The low content of sugar is a common problem in fruits of early ripening citrus in Yunnan Province. On the basis of exploring the regularity of sugar change in citrus fruits, the effects of leaves on fruiting branches on the accumulation of sugar in early ripening citrus were studied, with the aim to provide reference for research and development of the cultivation technology to improve the sugar content of citrus fruits.

Method The changes of enzyme activities related to sugar metabolism (S-AI, SPS and SS activities) of leaves and fruits of leaves number on different fruiting branches of ‘Okitsu wase’, and the corresponding content changes of fruit sugar composition (fructose, sucrose and glucose) were determined.

Result The content of glucose and total sugar in fruit juice sacs with four and seven leaves was higher than that of fruit with 1 leaf; sucrose phosphate synthase activity (SPS) in juice sacs increased with the accumulation of soluble sugar, while enzyme activity related to sucrose metabolism (S-AI, SPS and SS activities) in leaves was opposite; sucrose synthase activity (SS) in leaves was highly negatively correlated with sucrose and glucose content in sucrose juice sacs, and acid invertase (S-AI) in leaves was highly negatively correlated with glucose content in sucrose sacs; SPS activity in juice sacs was moderately positively correlated with glucose and sucrose content.

Conclusion The sugar content of citrus fruits obviously increased with the increase of the number of leaves on fruiting branches. The research and development of the management of fertilizer and water based on its fruits of the fruit-bearing branches with more leaves and flower and fruit management technology can improve the sugar content of early ripening citrus in Yunnan Province.