Psy (phytoene synthase)is an essential gene,to Psy gene, expression levels of the control groups were lowest among all treatment groups on day 5, and increased on day 10, but it was not highest, and then decreased on day 15; subsequently, it retained stable status on day 20; and Psy gene expression levels of the LD group were increased from the 5th day to the 15th day; for the SD group, Psy gene expression level was always lower from the 10th day to 20th day besides the 5th day; butit was worthwhile to note that Psy gene expression in the MD group was the highest during the periods of fruit development and ripening.