Citrus is one of the most important fruits in China. With general increase in yields of all kinds of fruits and melons, the fruit production in our country has changed from a situation where supply and demand were basically balanced to an excess of supply over demand. After entry of China into WTO, our domestic citrus market will surely face the competition from abroad. Therefore, the breeding and production of high quality citrus fruit is urgent. Sugars play an essential part in flavor character...